Auto merge of #113059 - Kobzol:ci-concurrency-fix, r=pietroalbini

CI: do not cancel concurrent builds on the same branch

Do not cancel concurrent builds on the same branch (outside of PRs).

Instead, only cancel them if the builds have the same commit SHA.

From the [documentation](https://docs.github.com/en/actions/learn-github-actions/contexts#github-context):
> The commit SHA that triggered the workflow. The value of this commit SHA depends on the event that triggered the workflow. For more information, see "[Events that trigger workflows](https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows)." For example, ffac537e6cbbf934b08745a378932722df287a53.

Fixes: rust-lang/rust#112955 (comment)

r? `@pietroalbini`

Author: bors