This updates our Gitea installation to 1.18.3. We bump our go verison to
1.19 to match upstream, disable some newer features in app.ini, and
synchronize our template files with upstream edits.
Otherwise not much stood out to me in the changelog as far as backward
compatibility goes:
https://github.com/go-gitea/gitea/blob/v1.18.3/CHANGELOG.md
Reviewers should look this over and double check that though.
Change-Id: I9679fb4908621a065ab3a0bc670a0e96ea15f476