Fix the build with -Zdirect-minimal-versions (nix-rust#2453)

The difference between -Zminimal-versions and -Zdirect-minimal-versions
is subtle.  But the important point is that with the former, a new
release published by one of our dependencies can cause our CI to fail.
With the latter, it cannot.  That's why I think it's better to test with
the latter.

.github/workflows/ci.yml

@@ -345,7 +345,7 @@ jobs:
         uses: dtolnay/rust-toolchain@nightly
 
       - name: setup 
-        run: cargo update -Zminimal-versions
+        run: cargo update -Zdirect-minimal-versions
 
       - name: check
         run: cargo check

Cargo.toml

@@ -29,7 +29,7 @@ targets = [
 
 [dependencies]
 libc = { version = "0.2.155", features = ["extra_traits"] }
-bitflags = "2.3.1"
+bitflags = "2.3.3"
 cfg-if = "1.0"
 pin-utils = { version = "0.1.0", optional = true }
 memoffset = { version = "0.9", optional = true }