Run releases rspec on both versions of component

This commit updates the feature specs for the Releases index page to
run twice - once with the `releases_index_apollo_client` feature flag
enabled, and once with it disabled.

app/assets/javascripts/releases/components/releases_sort_apollo_client.vue

@@ -76,6 +76,7 @@ export default {
   <gl-sorting
     :text="sortText"
     :is-ascending="isDirectionAscending"
+    data-testid="releases-sort"
     @sortDirectionChange="onDirectionChange"
   >
     <gl-sorting-item

spec/features/projects/releases/user_views_releases_spec.rb

@@ -15,11 +15,11 @@ RSpec.describe 'User views releases', :js do
   let_it_be(:guest) { create(:user) }
 
   before do
-    stub_feature_flags(releases_index_apollo_client: false)
     project.add_maintainer(maintainer)
     project.add_guest(guest)
   end
 
+  shared_examples 'releases index page' do
     context('when the user is a maintainer') do
       before do
         sign_in(maintainer)
@@ -145,4 +145,21 @@ RSpec.describe 'User views releases', :js do
         end
       end
     end
+  end
+
+  context 'when the releases_index_apollo_client feature flag is enabled' do
+    before do
+      stub_feature_flags(releases_index_apollo_client: true)
+    end
+
+    it_behaves_like 'releases index page'
+  end
+
+  context 'when the releases_index_apollo_client feature flag is disabled' do
+    before do
+      stub_feature_flags(releases_index_apollo_client: false)
+    end
+
+    it_behaves_like 'releases index page'
+  end
 end