Re-enable test_11g workflow with Ruby 4.0 only

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: yahonda

.github/workflows/test_11g.yml

@@ -1,7 +1,8 @@
 name: test_11g
 
 on:
-  workflow_dispatch:
+  push:
+  pull_request:
 
 jobs:
   build: