CI: Require schema job to pass (#15504)

I'm not certain, but I do not believe it was intentional in
#15000 to allow the `schema` job
to fail. This adds it to the required passing list.

Author: epage

.github/workflows/main.yml

@@ -27,6 +27,7 @@ jobs:
       - lockfile
       - resolver
       - rustfmt
+      - schema
       - test
       - test_gitoxide
     permissions: