New Test: [ iOS EWS ] fast/rendering/render-style-null-optgroup-crash.html is a flaky text failure (248923)

https://bugs.webkit.org/show_bug.cgi?id=248923
rdar://103099276

Unreviewed test gardening.

* LayoutTests/platform/ios/TestExpectations:

Canonical link: https://commits.webkit.org/257535@main

Author: robert-jenner

LayoutTests/platform/ios/TestExpectations

@@ -3795,3 +3795,5 @@ imported/w3c/web-platform-tests/screen-orientation/onchange-event-subframe.html
 webkit.org/b/248919 editing/selection/doubleclick-whitespace-live-range.html [ Failure ]
 
 webkit.org/b/248921 fast/forms/ios/focus-button.html [ Pass Crash ]
+
+webkit.org/b/248923 fast/rendering/render-style-null-optgroup-crash.html [ Pass Failure ]