chore(turbo): simplify contributing (vercel#8931)

### Description

Simplify contributing

### Testing Instructions

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  Give a quick description of steps to test your changes.
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CONTRIBUTING.md

@@ -2,8 +2,6 @@
 
 Thanks for your interest in contributing to Turbo!
 
-**Important note**: At the moment, Turbo is made up of two tools, Turborepo and Turbopack, built with different languages and toolchains. In the future, Turbo will become a single toolchain built on Rust and the Turbo engine. In the meantime, please follow the respective guide when contributing to each tool:
-
 - [Contributing to Turbo](#contributing-to-turbo)
   - [General Dependencies](#general-dependencies)
     - [Linux Dependencies](#linux-dependencies)
@@ -18,17 +16,12 @@ Thanks for your interest in contributing to Turbo!
   - [Manually testing `turbo`](#manually-testing-turbo)
   - [Publishing `turbo` to the npm registry](#publishing-turbo-to-the-npm-registry)
   - [Creating a new release blog post](#creating-a-new-release-blog-post)
-  - [Adding A New Crate](#adding-a-new-crate)
-  - [Contributing to Turbopack](#contributing-to-turbopack)
-    - [Turbopack Architecture](#turbopack-architecture)
-    - [Testing Turbopack](#testing-turbopack)
-    - [Profiling Turbopack](#profiling-turbopack)
   - [Troubleshooting](#troubleshooting)
 
 ## General Dependencies
 
 - [Rust](https://www.rust-lang.org/tools/install)
-- [cargo-groups](https://github.com/nicholaslyang/cargo-groups) (used to group crates into Turborepo-specific ones and Turbopack-specific ones)
+- [cargo-groups](https://github.com/nicholaslyang/cargo-groups)
 
 ### Linux Dependencies
 
@@ -187,122 +180,6 @@ turbo generate run "blog - "blog - update release post stats"
 
 and choose the blog post you would like to update.
 
-## Adding A New Crate
-
-When adding a new crate to the repo, it is essential that it is included/excluded from the
-relevant workflows. This ensures that changes to the crate are tested by the correct workflows,
-but that they do not trigger unnecessary workflows as well.
-
-First, determine whether the crate is for Turbopack or Turborepo. If it is for Turbopack, then the crate
-should be added to the `default-members` key in the root `Cargo.toml`. If the crate is for Turborepo, the
-crate must be added to the `PATTERNS` list in "Turborepo related changes" section of the `test.yml`
-workflow file. It must also be excluded from the "Turbopack related changes" section of the
-`test.yml` workflow file.
-
-For instance, if we were adding a `turborepo-foo` crate, we would add the following patterns:
-
-```diff
-      - name: Turbopack related changes
-        id: turbopack
-        uses: technote-space/get-diff-action@v6
-        with:
-          PATTERNS: |
-            pnpm-lock.yaml
-            package.json
-            crates/**
-            xtask/**
-            .cargo/**
-            rust-toolchain
-            !crates/turborepo/**
-            !crates/turborepo-lib/**
-            !crates/turborepo-ffi/**
-            !crates/turbo-updater/**
-+           !crates/turborepo-foo/**
-            !**.md
-            !**.mdx
-
-      - name: Turborepo related changes
-        id: turborepo
-        uses: technote-space/get-diff-action@v6
-        with:
-          PATTERNS: |
-            pnpm-lock.yaml
-            package.json
-            crates/turborepo/**
-            crates/turborepo-lib/**
-            crates/turborepo-ffi/**
-            crates/turbo-updater/**
-+           crates/turborepo-foo/**
-            .cargo/**
-            rust-toolchain
-            !**.md
-            !**.mdx
-```
-
-The crate must also be explicitly excluded from build commands
-for Turbopack and included in build commands for Turborepo.
-To do so, add a `--exclude turborepo-foo` flag to the Turbopack commands in
-`.cargo/config.toml` such as `tp-test`, and add an `-p turborepo-foo` to the Turborepo
-commands such as `tr-test`.
-
-Finally, the crate must be added to the Turborepo section of CODEOWNERS:
-
-```diff
-# overrides for crates that are owned by turbo-oss
-  /crates/turborepo @vercel/turbo-oss
-  /crates/turborepo-ffi @vercel/turbo-oss
-+ /crates/turborepo-foo @vercel/turbo-oss
-  /crates/turborepo-lib @vercel/turbo-oss
-  /crates/turborepo-scm @vercel/turbo-oss
-  /crates/turbo-updater @vercel/turbo-oss
-```
-
-## Contributing to Turbopack
-
-Turbopack uses [Cargo workspaces][workspaces] in the Turbo monorepo. You'll find
-several workspaces inside the `crates/` directory. In order to run a particular
-crate, you can use the `cargo run -p [CRATE_NAME]` command.
-
-### Turbopack Architecture
-
-A high-level introduction to Turbopack's architecture, workspace crates, and Turbo engine (the turbo-tasks crates) is available at [crates/turbopack/architecture.md](crates/turbopack/architecture.md).
-
-### Testing Turbopack
-
-Install `cargo-nextest` (https://nexte.st/):
-
-`cargo install cargo-nextest`
-
-Then, install dependencies for testcases:
-
-`pnpm install -r --side-effects-cache -C crates/turbopack/tests/node-file-trace`
-
-Run via:
-
-```shell
-cargo nextest run
-```
-
-For the test cases you need to run `pnpm install` to install some node_modules. See [Troubleshooting][] for solutions to common problems.
-
-You can also create a little demo app and run
-
-```shell
-cargo run -p node-file-trace -- print demo/index.js
-```
-
-Updating snapshot tests:
-
-In case of changes that involve updating snapshots you can use the `UPDATE=1` environment variable.
-
-```
-UPDATE=1 cargo nextest run
-```
-
-### Profiling Turbopack
-
-See [the profiling docs for Turbopack](https://turbo.build/pack/docs/advanced/profiling) for details.
-
 ## Troubleshooting
 
 See [Troubleshooting][].