Fix usage of cla-verification-action

Author: WojciechMazur

.github/workflows/cla.yml

@@ -4,6 +4,6 @@ jobs:
   check:
     runs-on: ubuntu-latest
     steps:
-    - uses: scala/cla-verification-action
+    - uses: scala/cla-verification-action@main
       with:
         author: ${{ github.event.pull_request.user.login }}