Fix component owner workflow permissions (open-telemetry#3165)

Author: jsoref

.github/workflows/component-owners.yml

@@ -10,6 +10,10 @@ jobs:
   run_self:
     runs-on: ubuntu-latest
     name: Auto Assign Owners
+    permissions: 
+      contents: read          # to read changed files 
+      issues: write           # to read/write issue assignees 
+      pull-requests: write    # to read/write PR reviewers 
     # Don't fail tests if this workflow fails. Some pending issues:
     # - https://github.com/dyladan/component-owners/issues/8
     continue-on-error: true