git: Enable bundled Git v2.35.1.gl1 by default

With b547b368 (git: Support bundled Git v2.35.1.gl1, 2022-02-22) we have introduced support fur bundled Git v2.35.1.gl1. The flag was subsequently rolled out on 2022-03-23. While there had been initial issues with repositories which had preexisting corrupted references, which were uncovered by this upgrade, the rollout went along smoothly otherwise.

Let's enable this new Git version by default. Note that this will cause us to also use the new Git version in background jobs, which aren't covered right now because we don't support feature flags in there.

Changelog: changed

Part of #4087 (closed)