[chore] update permissions to read only (#11974)

This workflow only needs read access.

Signed-off-by: Alex Boten <223565+codeboten@users.noreply.github.com>

.github/workflows/check-merge-freeze.yml

@@ -2,11 +2,22 @@ name: Merge freeze
 
 on:
   pull_request:
-    types: [opened, ready_for_review, synchronize, reopened, labeled, unlabeled, enqueued]
+    types:
+      [
+        opened,
+        ready_for_review,
+        synchronize,
+        reopened,
+        labeled,
+        unlabeled,
+        enqueued,
+      ]
     branches: [main]
   merge_group:
     types: [checks_requested]
 
+permissions: read-all
+
 jobs:
   check-merge-freeze:
     name: Check