Remove feature flag search_sort_issues_by_popularity

Changelog: added

app/helpers/search_helper.rb

@@ -150,7 +150,7 @@ module SearchHelper
       }
     ]
 
-    if search_service.scope == 'issues' && Feature.enabled?(:search_sort_issues_by_popularity)
+    if search_service.scope == 'issues'
       options << {
         title: _('Popularity'),
         sortable: true,

app/views/search/results/_issuable.html.haml

@@ -12,7 +12,7 @@
     .description.term.gl-px-0
       = highlight_and_truncate_issuable(issuable, @search_term, @search_highlight)
   .col-sm-3.gl-mt-3.gl-sm-mt-0.gl-text-right
-    - if Feature.enabled?(:search_sort_issues_by_popularity) && issuable.respond_to?(:upvotes_count) && issuable.upvotes_count > 0
+    - if issuable.respond_to?(:upvotes_count) && issuable.upvotes_count > 0
       %li.issuable-upvotes.gl-list-style-none.has-tooltip{ title: _('Upvotes') }
         = sprite_icon('thumb-up', css_class: "gl-vertical-align-middle")
         = issuable.upvotes_count

config/feature_flags/development/search_sort_issues_by_popularity.yml

----
-name: search_sort_issues_by_popularity
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/65231
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/334974
-milestone: '14.1'
-type: development
-group: group::global search
-default_enabled: false