Fix bad rubocop auto-correct in engine.rb

Signed-off-by: Alex Coles <alex@alexbcoles.com>

lib/open_project/backlogs/engine.rb

@@ -108,7 +108,7 @@ module OpenProject::Backlogs
            caption: :project_module_backlogs,
            before: :calendar,
            param: :project_id,
-           if: proc { notUser.current.respond_to?(:impaired?) and User.current.impaired? },
+           if: proc { not(User.current.respond_to?(:impaired?) and User.current.impaired?) },
            html: { class: 'icon2 icon-backlogs-icon' }
     end