Set supported version

Author: ksss

gems/activesupport/.rubocop.yml

@@ -1,8 +1,15 @@
 inherit_from: ../../.rubocop.yml
 
+# Please specify only supported versions.
 RBS/Layout:
   Enabled: true
+  Include:
+    - "gems/activesupport/7.0/**/*.rbs"
 RBS/Lint:
   Enabled: true
+  Include:
+    - "gems/activesupport/7.0/**/*.rbs"
 RBS/Style:
   Enabled: true
+  Include:
+    - "gems/activesupport/7.0/**/*.rbs"