WindowManager: Don't pass 'this' to window factory method
WindowManager: Don't pass 'this' to window factory method

Added in 3ba36b9a (The great and terrible dialog refactor), no longer
needed after 466a8762 (Make content isolation optional) which removed
manager as an argument to window.

This broke things after we allowed Element to accept '$element' as
config parameter in 883678d6 (Implement OO.ui.infuse to reconstitute
PHP widgets in client-side JS).

Bug: T90858
Change-Id: Ifab2aad63d5b9eef64541a332235c8f9ad3fc765

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui