ci: Rule out scheduled pipelines in .windows-build-rules

The lack of this broke scheduled pipelines, because they attempted
to create a meson-windows-vs2019 job, which couldn't work (because the
windows_build_vs2019 job doesn't exist in scheduled pipelines).

Fixes: 84c8a35aa2 "CI: Add Windows source dependency map"
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8360>

.gitlab-ci/test-source-dep.yml

@@ -238,6 +238,7 @@
 # rules duplication manually
 .windows-build-rules:
   rules:
+    - *ignore_scheduled_pipelines
     - changes: 
         *mesa_core_file_list
       when: on_success