ci: nightly ci now uses ubuntu 24.04+ (#2886)

which needs user namespaces to be re-enabled so that stacker can
build/run

Signed-off-by: Ramkumar Chinchani <rchincha.dev@gmail.com>

.github/workflows/nightly.yaml

@@ -196,6 +196,7 @@ jobs:
           password: ${{ github.token }}
       - name: Run tests
         run: |
+            sudo ./scripts/enable_userns.sh
             ./examples/kind/kind-ci.sh
 
   cloud-scale-out: