Removes RemoteMirror related TODO from project_spec

spec/models/project_spec.rb

@@ -1885,8 +1885,6 @@ describe Project do
       update_remote_mirrors
     end
 
-    # TODO: study if remote_mirror_available_overridden is still a necessary attribute considering that
-    # it is no longer under any license
     it 'does nothing when remote mirror is disabled globally and not overridden' do
       stub_application_setting(mirror_available: false)
       project.remote_mirror_available_overridden = false