chore: update workflow permissions to read-only (#12691)

Fixes #<issue_number_goes_here> 🦕

---------

Co-authored-by: Anthonios Partheniou <partheniou@google.com>

Author: ohmayr

.github/workflows/main.yml

@@ -21,8 +21,7 @@ on:
     # Run this Github Action every Tuesday at 7 AM UTC
     - cron:  '0 7 * * 2'
 
-permissions:
-  contents: read
+permissions: read-all
 
 jobs:
   build: