Dropdown data-api vs js inconsistency fix

Changed selector for clearMenus() - "[data-toggle=dropdown]" was taking only data-api dropdowns into account, changed to ".dropdown-toggle" because its needed in all dropdowns for proper styling

Removed reduntant event hook in constructor (leaved empty constructor) - clearMenus runs on html so it clears all

Bug [#8104](https://github.com/twitter/bootstrap/issues/8104)