Add and apply RSpec/EmptyHook rule

This rule was added in rubocop-rspec 1.39.0. Now leaving an empty block
by accident like I did in commit 91c21b09 is harder :).

.rubocop.yml

@@ -327,6 +327,9 @@ RSpec/EmptyExampleGroup:
   Exclude:
     - spec/factories/**/*
 
+RSpec/EmptyHook:
+  Enabled: true
+
 RSpec/EmptyLineAfterExample:
   Enabled: true
 

spec/system/votes_spec.rb

@@ -4,9 +4,6 @@ describe "Votes" do
   let!(:verified)   { create(:user, verified_at: Time.current) }
   let!(:unverified) { create(:user) }
 
-  before do
-  end
-
   describe "Debates" do
     before { login_as(verified) }