docs-builder: add pull-requests: write permission to docs-build workflow (#8603)

(cherry picked from commit 7cf538c)

Author: reakaleek

.github/workflows/docs-build.yml

@@ -16,4 +16,4 @@ jobs:
       deployments: write
       id-token: write
       contents: read
-      pull-requests: read
+      pull-requests: write