Remove buy_storage_link feature flag

Permanently enables purchase more storage button in usage quotas page

ee/app/helpers/ee/namespace_storage_limit_alert_helper.rb

@@ -47,7 +47,6 @@ module EE
     end
 
     def purchase_storage_link_enabled?(namespace)
-      ::Feature.enabled?(:buy_storage_link) &&
       namespace.additional_repo_storage_by_namespace_enabled?
     end
 

ee/changelogs/unreleased/remove-buy-storage-link-feature-flag.yml

+---
+title: Add purchase more storage button to storage usage quotas page
+merge_request: 55246
+author:
+type: added

ee/config/feature_flags/development/buy_storage_link.yml

----
-name: buy_storage_link
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/35360
-rollout_issue_url: 
-milestone: '13.2'
-type: development
-group: group::fulfillment
-default_enabled: false

ee/spec/helpers/ee/namespace_storage_limit_alert_helper_spec.rb

@@ -165,16 +165,13 @@ RSpec.describe EE::NamespaceStorageLimitAlertHelper do
 
     let_it_be(:namespace) { build(:namespace) }
 
-    where(:buy_storage_link_enabled, :additional_repo_storage_by_namespace_enabled, :result) do
-      false | false | false
-      false | true  | false
-      true  | false | false
-      true  | true  | true
+    where(:additional_repo_storage_by_namespace_enabled, :result) do
+      false | false
+      true  | true
     end
 
     with_them do
       before do
-        stub_feature_flags(buy_storage_link: buy_storage_link_enabled)
         allow(namespace).to receive(:additional_repo_storage_by_namespace_enabled?)
           .and_return(additional_repo_storage_by_namespace_enabled)
       end