Remove mention to setup-buildx-action

README.md

@@ -109,7 +109,6 @@ to the default Git context:
           tags: user/app:latest
 ```
 > :warning: Subdirectory for Git context is only available from [Buildkit version 0.9.0](https://github.com/moby/buildkit/releases/tag/v0.9.0).
-You can resort to the [setup-buildx-action action](https://github.com/docker/setup-buildx-action) to upgrade Buildkit as the version present in the [public Github runners is quite outdated](https://github.com/docker/build-push-action/issues/591#issuecomment-1093159996).
 
 Building from the current repository automatically uses the [GitHub Token](https://help.github.com/en/actions/configuring-and-managing-workflows/authenticating-with-the-github_token)
 so it does not need to be passed. If you want to authenticate against another