Remove instructions for bintray migration

Bintray stopped working 1 year ago (May 2021), so these instructions are no longer necessary.

README.md

@@ -104,27 +104,6 @@ sudo dnf install k6    # use yum install --nogpgcheck k6 for older distros (e.g.
 Note that the `gnupg2` package is required for signature verification.
 
 
-#### Migrating from Bintray
-
-The Bintray repositories were [shut down after May 1st, 2021](https://jfrog.com/blog/into-the-sunset-bintray-jcenter-gocenter-and-chartcenter/). If you previously added them, you will have to add our repositories following the instructions above and should delete the Bintray ones.
-
-For Debian-based distributions, you can run:
-
-```bash
-sudo sed -i '/dl\.bintray\.com\/loadimpact\/deb/d' /etc/apt/sources.list
-sudo apt-key del 379CE192D401AB61
-sudo apt-get update
-```
-
-Or delete the repository file if you added it to `/etc/apt/sources.list.d/`.
-
-And for rpm-based ones, delete the repository file in `/etc/yum.repos.d/`. If you followed the [official installation instructions](https://k6.io/docs/getting-started/installation/#fedora-centos), this should be:
-
-```bash
-sudo rm /etc/yum.repos.d/bintray-loadimpact-rpm.repo
-```
-
-
 ### Docker
 
 ```bash