ci: Update GitHub workflows

.github/workflows/specs_rails70.yml

@@ -15,11 +15,10 @@ jobs:
 
     strategy:
       matrix:
-        ruby: ['3.3']
-        gemfile: ['rails70_activeadmin']
+        ruby: ['3.1']
 
     env:
-      BUNDLE_GEMFILE: ${{ github.workspace }}/gemfiles/${{ matrix.gemfile }}.gemfile
+      RAILS_VERSION: 7.0.0
 
     steps:
       - name: Checkout repository