devops: fix cherry_pick_into_release_branch permissions (#29689)

Fixes
https://github.com/microsoft/playwright/actions/runs/8067553095/job/22038251156.

Signed-off-by: Max Schmitt <max@schmitt.mx>

Author: mxschmitt

.github/workflows/cherry_pick_into_release_branch.yml

@@ -12,6 +12,9 @@ on:
         description: Comma-separated list of commit hashes to cherry-pick
         required: true
 
+permissions:
+  contents: write
+
 jobs:
   roll:
     runs-on: ubuntu-22.04