drop pr approver workflow top-level permissions

Set top-level permissions to none. This is the best practice for
GH actions, and for example OpenSSF Scorecards penalize CAPI for
not having it.

Signed-off-by: Tuomo Tanskanen <[email protected]>

Author: tuminoid

.github/workflows/pr-gh-workflow-approve.yaml

@@ -8,6 +8,8 @@ on:
       - reopened
       - synchronize
 
+permissions: {}
+
 jobs:
   approve:
     name: Approve ok-to-test