Fixed permissions for GitHub action with welcome message.

Follow up to bc33b047848759e7ae90bf85c94ff6cc5913e1ee.

.github/workflows/new_contributor_pr.yml

@@ -5,7 +5,7 @@ on:
     types: [opened]
 
 permissions:
-  pull-requests: [read, write]
+  pull-requests: write
 
 jobs:
   build: