Install skopeo in e2e test workflow

The middleware update test uses skopeo to inspect OCI image labels
and verify the middleware-version was updated.

Author: creydr

.github/workflows/test-e2e.yml

@@ -33,6 +33,12 @@ jobs:
       - name: Install helm
         uses: azure/setup-helm@v4.3.0
 
+        # skopeo is needed in the middleware e2e tests to inspect OCI image labels
+      - name: Install skopeo
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y skopeo
+
         # func CLI is needed in some e2e tests ATM
       - name: Install func cli
         uses: functions-dev/action@main