ci: add missing permissions to .github/workflows/plugins-check.yml (#6790)

This might be the cause of
https://github.com/firebase/firebase-android-sdk/actions/runs/13979443579/job/39141224363?pr=6789


Update: confirmed in
https://github.com/firebase/firebase-android-sdk/actions/runs/13979884815/job/39142572824?pr=6790

---------

Co-authored-by: Rodrigo Lazo <[email protected]>

Author: thatfiredev

.github/workflows/plugins-check.yml

@@ -11,6 +11,9 @@ concurrency:
 
 jobs:
   plugins-check:
+    permissions:
+      checks: write
+      pull-requests: write
     runs-on: ubuntu-22.04
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2