use bash when relying on bash features

.forgejo/workflows/actions.yaml

@@ -123,6 +123,7 @@ jobs:
 
       - name: Extract commit message
         id: extract_commit_message
+        shell: bash # `@Q` is bash exclusive
         run: |
           COMMIT_MESSAGE=$(git log --format=%B -n 1 $GITHUB_SHA)
           ESCAPED_COMMIT_MESSAGE="${COMMIT_MESSAGE@Q}"
@@ -130,10 +131,9 @@ jobs:
 
       - name: Check commit message
         id: check_commit_message
-        shell: bash
         run: |
           COMMIT_MESSAGE="${{ steps.extract_commit_message.outputs.message }}"
-          OUTPUT="$(python .forgejo/workflows/scripts/message.py "${COMMIT_MESSAGE@Q}")"
+          OUTPUT="$(python .forgejo/workflows/scripts/message.py "${COMMIT_MESSAGE}")"
           if [ "$OUTPUT" = "Usage: python message.py <commit_message>" ]; then
             echo "Called without commit message!"
             exit 1