Test 3.0 stable branch only for Foreman 3.11 and 3.12

.github/workflows/ruby.yml

@@ -3,7 +3,7 @@ name: Ruby Tests
 on:
   push:
     branches:
-      - main
+      - 3.0-stable
   pull_request:
 
 concurrency:
@@ -20,7 +20,6 @@ jobs:
       fail-fast: false
       matrix:
         foreman:
-          - develop
           - 3.12-stable
           - 3.11-stable
     needs: rubocop