Revert "Add action to check for fixup commits"

Signed-off-by: Daniel Kesselberg <mail@danielkesselberg.de>

.github/workflows/fixup.yml

@@ -1,13 +0,0 @@
-on: pull_request
-
-name: Pull request checks
-
-jobs:
-  commit-message-check:
-    name: Block fixup and squash commits
-    runs-on: ubuntu-latest
-    steps:
-      - name: Run check
-        uses: xt0rted/block-autosquash-commits-action@main
-        with:
-          repo-token: ${{ secrets.GITHUB_TOKEN }}