Use linear version GroupsWithTemplatesFinder#extended_group_search

config/feature_flags/development/linear_groups_template_finder_extended_group_search.yml

----
-name: linear_groups_template_finder_extended_group_search
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68936
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/339439
-milestone: '14.3'
-type: development
-group: group::access
-default_enabled: false

ee/app/finders/groups_with_templates_finder.rb

@@ -18,6 +18,7 @@ class GroupsWithTemplatesFinder
   attr_reader :group_id
 
   def extended_group_search
+    # We're adding an extra query that will be removed once we remove the feature flag in https://gitlab.com/gitlab-org/gitlab/-/issues/339439
     groups = if Feature.enabled?(:linear_groups_template_finder_extended_group_search_ancestors_scopes, current_group, default_enabled: :yaml)
                Group.with_project_templates.self_and_ancestors
              else
@@ -26,14 +27,7 @@ class GroupsWithTemplatesFinder
                  .base_and_ancestors
              end
 
-    groups_with_plan = groups.with_feature_available_in_plan(:group_project_templates)
-
-    # We're adding an extra query that will be removed once we remove the feature flag in https://gitlab.com/gitlab-org/gitlab/-/issues/339439
-    if ::Feature.enabled?(:linear_groups_template_finder_extended_group_search, current_group, default_enabled: :yaml)
-      groups_with_plan.self_and_descendants
-    else
-      Gitlab::ObjectHierarchy.new(groups_with_plan).base_and_descendants
-    end
+    groups.with_feature_available_in_plan(:group_project_templates).self_and_descendants
   end
 
   def simple_group_search(groups)

ee/spec/finders/groups_with_templates_finder_spec.rb

@@ -99,14 +99,6 @@ RSpec.describe GroupsWithTemplatesFinder, :saas do
 
   it_behaves_like 'group template finder examples'
 
-  context 'when feature flag :linear_groups_template_finder_extended_group_search is disabled' do
-    before do
-      stub_feature_flags(linear_groups_template_finder_extended_group_search: false)
-    end
-
-    it_behaves_like 'group template finder examples'
-  end
-
   context 'when feature flag :linear_groups_template_finder_extended_group_search_ancestors_scopes is disabled' do
     before do
       stub_feature_flags(linear_groups_template_finder_extended_group_search_ancestors_scopes: false)
@@ -114,13 +106,4 @@ RSpec.describe GroupsWithTemplatesFinder, :saas do
 
     it_behaves_like 'group template finder examples'
   end
-
-  context 'when all linear feature flags are disabled' do
-    before do
-      stub_feature_flags(linear_groups_template_finder_extended_group_search: false)
-      stub_feature_flags(linear_groups_template_finder_extended_group_search_ancestors_scopes: false)
-    end
-
-    it_behaves_like 'group template finder examples'
-  end
 end