update actions permissions

Author: vuolen

.github/workflows/pull_request.yml

@@ -5,6 +5,9 @@ jobs:
   preview:
     name: Pulumi Preview
     runs-on: ubuntu-latest
+    permissions:
+      contents: "read"
+      id-token: "write"
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5