Merge branch 'default-attempt-project-search' into 'master'

Set attempt project search optimizations flag to default_enabled

Closes #60452

See merge request gitlab-org/gitlab-ce!28474

app/finders/issuable_finder.rb

@@ -346,7 +346,7 @@ class IssuableFinder
 
   def attempt_project_search_optimizations?
     params[:attempt_project_search_optimizations] &&
-      Feature.enabled?(:attempt_project_search_optimizations)
+      Feature.enabled?(:attempt_project_search_optimizations, default_enabled: true)
   end
 
   def count_key(value)