Update docker.io/postgres Docker tag to v18

.gitea/workflows/render-manifests.yaml

@@ -16,6 +16,9 @@ env:
 jobs:
   render-manifests-helm:
     runs-on: ubuntu-js
+    permissions:
+      contents: write
+      pull-requests: write
     steps:
       - name: Checkout
         uses: actions/checkout@v6