feat(gitter): /tags always resolve to commit hash

[Ly-Joey]

Gitter's /tag endpoint, added in #5181, does minimal handling for annotated tags.

When tags are annotated (git tag with -a, -s, or -u), git creates a separate tag object to contain metadata (tagger, date, etc) with its own hash.
This results in annotated tags effectively resolving to two objects when we do ls-remote or show-ref

• ref/tags/tag-name: the tag object
• ref/tags/tag-name^{}: the peeled commit hash the tag is actually pointing to

Take https://github.com/ossf/scorecard as an example, gitter's response will contain:

{ "label": "v5.4.0", "hash": "FULSTmQUBv/amP3sUMXuB9JHJiY=" } <- Don't use this
{ "label": "v5.4.0^{}", "hash": "gO4+z+34sZq4mRcTqf2y59zXJi4=" } <- Use this

The only reason to return the tag object hash was to keep Gitter's output consistent with the git binary.
Since the tag object isn't useful downstream and might actually cause unnecessary confusion / issues, we're removing it entirely.

From now on, the resolved hash linked to a tag name will always be a commit.