git: Make Git v2.35.1.gl1 the default Git distribution

With this MR we're removing the feature flag we had for bundled Git v2.35.1.gl1. Now that we have tested this version in production we also upgrade the default Git distribution to the same version so that users who don't use bundled Git yet can benefit from this upgrade.

Note that we do not yet remove bundled Git v2.33.1.gl1 from our Makefile: it's still required to stay for a release so that zero-downtime upgrades aren't impacted by removal of these binaries.

Closes #4087 (closed)