fix: add pull-requests write permission for automated PR creation (#252)

Adds pull-requests: write permission to fix the GraphQL: Resource not
accessible by integration (createPullRequest) error when the workflow
tries to create pull requests for feature tracker updates.

Author: lgallard

.github/workflows/feature-discovery.yml

@@ -32,6 +32,7 @@ jobs:
     permissions:
       contents: write
       issues: write
+      pull-requests: write
       actions: read
       id-token: write