Remove shared_group_membership_auth feature flag

Display of shared groups bug has been fixed. No need for the FF any
longer.

app/models/user.rb

@@ -940,11 +940,7 @@ class User < ApplicationRecord
   # Returns the groups a user has access to, either through a membership or a project authorization
   def authorized_groups
     Group.unscoped do
-      if Feature.enabled?(:shared_group_membership_auth, self)
       authorized_groups_with_shared_membership
-      else
-        authorized_groups_without_shared_membership
-      end
     end
   end
 

changelogs/unreleased/alexpooley-remove_shared_group_membership_auth_ff.yml

+---
+title: Include shared with groups in list of authorized groups
+merge_request: 54894
+author:
+type: fixed

config/feature_flags/development/shared_group_membership_auth.yml

----
-name: shared_group_membership_auth
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/46412
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/224771
-milestone: '13.6'
-type: development
-group: group::access
-default_enabled: false

spec/models/user_spec.rb

@@ -3234,24 +3234,9 @@ RSpec.describe User do
         create(:group_group_link, shared_group: private_group, shared_with_group: other_group)
       end
 
-      context 'when shared_group_membership_auth is enabled' do
-        before do
-          stub_feature_flags(shared_group_membership_auth: user)
-        end
-
       it { is_expected.to include shared_group }
       it { is_expected.not_to include other_group }
     end
-
-      context 'when shared_group_membership_auth is disabled' do
-        before do
-          stub_feature_flags(shared_group_membership_auth: false)
-        end
-
-        it { is_expected.not_to include shared_group }
-        it { is_expected.not_to include other_group }
-      end
-    end
   end
 
   describe '#membership_groups' do