ci: Temporarily run the FreeBSD on a schedule rather than every commit

The runner is currently offline and we can’t have that blocking
development.

See: https://gitlab.gnome.org/Infrastructure/Infrastructure/-/issues/1503

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

.gitlab-ci.yml

@@ -602,7 +602,7 @@ vs2017-x64-static:
       - _build/meson-logs
 
 freebsd-13-x86_64:
-  extends: .only-origin-or-manual
+  extends: .only-schedules-or-manual
   stage: build
   tags:
     - freebsd-13