Remove cache_merge_to_ref_calls feature flag

Changelog: performance

app/services/merge_requests/merge_to_ref_service.rb

@@ -66,8 +66,7 @@ module MergeRequests
     end
 
     def commit(cache_merge_to_ref_calls = false)
-      if cache_merge_to_ref_calls &&
-        Feature.enabled?(:cache_merge_to_ref_calls, project, default_enabled: false)
+      if cache_merge_to_ref_calls
         Rails.cache.fetch(cache_key, expires_in: 1.day) do
           extracted_merge_to_ref
         end

config/feature_flags/development/cache_merge_to_ref_calls.yml

----
-name: cache_merge_to_ref_calls
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/67789
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/338251
-milestone: '14.2'
-type: development
-group: group::code review
-default_enabled: false

spec/services/merge_requests/merge_to_ref_service_spec.rb

@@ -37,23 +37,21 @@ RSpec.describe MergeRequests::MergeToRefService do
       expect(ref_head.id).to eq(result[:commit_id])
     end
 
-    context 'cache_merge_to_ref_calls flag enabled', :use_clean_rails_memory_store_caching do
+    context 'cache_merge_to_ref_calls parameter', :use_clean_rails_memory_store_caching do
       before do
-        stub_feature_flags(cache_merge_to_ref_calls: true)
-
         # warm the cache
         #
         service.execute(merge_request, true)
       end
 
-      context 'when cache_merge_to_ref_calls parameter is true' do
+      context 'when true' do
         it 'caches the response', :request_store do
           expect { 3.times { service.execute(merge_request, true) } }
             .not_to change(Gitlab::GitalyClient, :get_request_count)
         end
       end
 
-      context 'when cache_merge_to_ref_calls parameter is false' do
+      context 'when false' do
         it 'does not cache the response', :request_store do
           expect(Gitlab::GitalyClient).to receive(:call).at_least(3).times.and_call_original
 
@@ -61,24 +59,6 @@ RSpec.describe MergeRequests::MergeToRefService do
         end
       end
     end
-
-    context 'cache_merge_to_ref_calls flag disabled', :use_clean_rails_memory_store_caching do
-      before do
-        stub_feature_flags(cache_merge_to_ref_calls: false)
-
-        # warm the cache
-        #
-        service.execute(merge_request, true)
-      end
-
-      [true, false].each do |cache_merge_to_ref_calls|
-        it 'does not cache the response, regardless of cache_merge_to_ref_calls state', :request_store do
-          expect(Gitlab::GitalyClient).to receive(:call).at_least(3).times.and_call_original
-
-          3.times { service.execute(merge_request, cache_merge_to_ref_calls) }
-        end
-      end
-    end
   end
 
   shared_examples_for 'successfully evaluates pre-condition checks' do