.github/workflows/labeler.yml: pin action by sha

This action has write access to PRs so we should guard against a
compromised tag and only update explicitly via renovate PRs.

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

Author: Luap99

.github/workflows/labeler.yml

@@ -10,4 +10,4 @@ jobs:
       pull-requests: write
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/labeler@v6
+    - uses: actions/labeler@f27b608878404679385c85cfa523b85ccb86e213 # v6