add write permission for signing job

Author: sean-breen

.github/workflows/assertion.yml

@@ -26,7 +26,7 @@ jobs:
     runs-on: ubuntu-22.04
     if: ${{ !github.event.pull_request.head.repo.fork }}
     permissions:
-      contents: read
+      contents: write
     env:
       GOPROXY: "https://${{ secrets.ARTIFACTORY_USER }}:${{ secrets.ARTIFACTORY_TOKEN }}@azr.artifactory.f5net.com/artifactory/api/go/f5-nginx-go-dev"
     outputs: