[ci] Temporarily run agent-network e2e on push to this branch

Revert before merge; the workflow_dispatch API is not available to the
automation that needs to trigger the run.

.github/workflows/agent-network-e2e.yml

@@ -5,6 +5,10 @@ on:
   schedule:
     - cron: "0 3 * * *"
   workflow_dispatch:
+  # TEMPORARY: run on push to this branch to validate the DNS lazy-connection
+  # warm-up end to end. Revert before merge.
+  push:
+    branches: ["feature/dns-lazy-conn-warmup"]
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}