Include the base URI in the `g_test_bug()` calls instead. This resolves
inconsistencies between the old bug base (bugzilla.gnome.org) and the
new bug base (gitlab.gnome.org). It also has the advantage that the URI
passed to `g_test_bug()` is now clickable in the code editor, rather
than being split across two locations.
See https://gitlab.gnome.org/GNOME/glib/-/merge_requests/275#note_303175
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>