ci: Improve commit message lint

Improve the commit message check, by logging only the commit title, and
doing away with the extra spaces.

.github/workflows/check_push.yml

@@ -16,4 +16,4 @@ jobs:
           run: |
             git fetch origin
             git status
-            git log origin/main..HEAD | grep -ie '^    fixup\|^    wip' && exit 1 || true
+            git log --pretty=format:%s origin/main..HEAD | grep -ie '^fixup\|^wip' && exit 1 || true