platform/ios/mediastream/video-muted-in-background-tab.html causes cr…

…ashes in subsequent tests

https://bugs.webkit.org/show_bug.cgi?id=264063
rdar://27990301

Unreviewed test gardening.

In EWS it's common to see crashes in tests that run after platform/ios/mediastream/video-muted-in-background-tab.html
(these are often scrollbar tests).

platform/ios/mediastream/video-muted-in-background-tab.html calls `window.internals.setPageVisibility(false)`
which seems to trigger this. When running locally, this test actually triggers a SpringBoard crash, and then
some subsequent test asserts in -[WebKitTestRunnerApp applicationDidEnterBackground:].

Skip this test until the issue is resolved.

* LayoutTests/platform/ios-wk2/TestExpectations:

Canonical link: https://commits.webkit.org/270089@main

LayoutTests/platform/ios-wk2/TestExpectations

@@ -2431,6 +2431,7 @@ imported/w3c/web-platform-tests/html/semantics/embedded-content/the-iframe-eleme
 # Requires grammar checking to be enabled (rdar://103646683)
 editing/selection/ios/show-grammar-replacements-on-tap.html [ Skip ]
 
+webkit.org/b/264063 platform/ios/mediastream/video-muted-in-background-tab.html [ Skip ]
 
 webkit.org/b/259524 media/audioSession/audioSessionState.html [ Pass Failure ]