Fix layout when MinimumWidth/HeightRequest is removed on Windows

[spadapet]

Description of Change

ViewExtensions.UpdateMinimumHeight|Width for WinUI is supposed to update FrameworkElement.MinHeight|Width based on the MAUI property MinimumHeightRequest/MinimumWidthRequest. But it would completely skip the update when the value was removed, so the previously set value would stay in effect. That locks in the old FrameworkElement.MinHeight|Width, and layout doesn't change.

The fix is to remove FrameworkElement.MinHeight|Width when MinimumHeightRequest/MinimumWidthRequest is removed.

Issues Fixed

Fixes #24638

[PureWeen]

test is faiing

https://dev.azure.com/xamarin/public/_build/results?buildId=123366&view=ms.vss-test-web.build-test-results-tab&runId=3123614&resultId=100011&paneView=debug

[spadapet]

test is faiing

https://dev.azure.com/xamarin/public/_build/results?buildId=123366&view=ms.vss-test-web.build-test-results-tab&runId=3123614&resultId=100011&paneView=debug

Ack, the test passed locally on Windows and Android. Maybe I need to request a smaller min width/height since the height ended up being 486 instead of 500.

@PureWeen