ci: Make clippy a required job

This was part of e09683e ("run clippy on 3 major platforms"), most
of which made it to libc-0.2. However, this line was missed.

Author: tgross35

.github/workflows/ci.yaml

@@ -304,6 +304,7 @@ jobs:
       - test_tier2_vm
       - verify_build
       - docs
+      - clippy
     # Github branch protection is exceedingly silly and treats "jobs skipped because a dependency
     # failed" as success. So we have to do some contortions to ensure the job fails if any of its
     # dependencies fails.