Remove redundant setting resets in after blocks

Settings are stored in the database, and so any changes to the settings
done during the tests are automatically rolled back between one test and
the next one.

There were also a few places where we weren't using an `after` block but
changing the setting at the end of the test.

spec/controllers/installation_controller_spec.rb

@@ -13,22 +13,12 @@ describe InstallationController, type: :request do
     let(:seeds_feature_settings) { Setting.where("key LIKE 'feature.%'") }
 
     before do
-      @current_feature_settings = seeds_feature_settings.pluck(:key, :value).to_h
       seeds_feature_settings.destroy_all
       test_feature_settings.each do |feature_name, feature_value|
         Setting["feature.#{feature_name}"] = feature_value
       end
     end
 
-    after do
-      test_feature_settings.each_key do |feature_name|
-        Setting.find_by(key: "feature.#{feature_name}").destroy
-      end
-      @current_feature_settings.each do |feature_name, feature_value|
-        Setting[feature_name] = feature_value
-      end
-    end
-
     specify "with query string inside query params" do
       get "/consul.json"