Remove unnecessary to_s.

Co-authored-by: Jan Sandbrink <j.sandbrink@openproject.com>

Author: mereghost

modules/wikis/app/models/queries/wikis/page_links/filter/provider_filter.rb

@@ -42,7 +42,7 @@ def human_name
           end
 
           def allowed_values
-            ::Wikis::Provider.enabled.pluck(:universal_identifier).map { |uid| [uid, uid.to_s] }
+            ::Wikis::Provider.enabled.pluck(:universal_identifier).map { |uid| [uid, uid] }
           end
 
           def left_outer_joins = :provider