Release cached merge_request show.json

Changelog: performance

app/controllers/projects/merge_requests_controller.rb

@@ -132,7 +132,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
       format.json do
         Gitlab::PollingInterval.set_header(response, interval: 10_000)
 
-        if params[:serializer] == 'sidebar_extras' && Feature.enabled?(:merge_request_show_render_cached, @project, default_enabled: :yaml)
+        if params[:serializer] == 'sidebar_extras'
           cache_context = [
             params[:serializer],
             current_user&.cache_key,

config/feature_flags/development/merge_request_show_render_cached.yml

----
-name: merge_request_show_render_cached
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/65217
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/335938
-milestone: '14.2'
-type: development
-group: group::code review
-default_enabled: false