Add and appy RSpec/RepeatedExampleGroupBody rule

This rule is available since rubocop-rspec 1.38.0. Thanks to it, we've
found out we were testing topics behave like notifiable twice.

.rubocop.yml

@@ -365,6 +365,9 @@ RSpec/OverwritingSetup:
 RSpec/RepeatedExample:
   Enabled: true
 
+RSpec/RepeatedExampleGroupBody:
+  Enabled: true
+
 RSpec/ScatteredLet:
   Enabled: true
 

spec/models/topic_spec.rb

@@ -68,8 +68,4 @@ describe Topic do
       expect(results).to eq [topic1, topic2, topic3]
     end
   end
-
-  describe "notifications" do
-    it_behaves_like "notifiable"
-  end
 end