For the same reasons as in Investigate renaming master git branch to main (#2348) · Issues · GNOME / GLib · GitLab, dconf’s master branch has now been renamed to main.
It will need to be updated on l10n.gnome.org.
If you have a local clone of dconf, you’ll need to update your checked out branches using:
git checkout master
git branch -m master main
git fetch
git branch --unset-upstream
git branch -u origin/main
git symbolic-ref refs/remotes/origin/HEAD refs/remotes/origin/main