In flutter/engine#40241, I added a workaround for an AppKit bug wherein mouseDown/Up events were ignored when the Reduced Transparency accessibility setting was enabled, and the view was hosted in an NSPopover.

I filed a Radar and Apple reported the bug fixed in macOS 13.3.1.

When we drop support for macOS 12 in Flutter, we should remove the workaround in
FlutterViewController, here:
https://github.com/flutter/engine/blob/3ce6c4bf17534fddb07ea98df035d33243d9fd7a/shell/platform/darwin/macos/framework/Source/FlutterViewController.mm#L289-L316

So long as nothing else has been added to these methods at that time, the method overrides themselves should be removed, so that we fall back to the default behaviour.

See: #115015
See: http://www.openradar.me/FB12050037
See: https://developer.apple.com/documentation/appkit/nsresponder/1535349-mouseup