Make MediaSourceUseRemoteAudioVideoRenderer testable

https://bugs.webkit.org/show_bug.cgi?id=302937
rdar://165204590

Reviewed by Youenn Fablet.

We can now start testing MediaSourceUseRemoteAudioVideoRenderer which makes
MSE entirely runs in the web content process.

Covered by existing tests.
* LayoutTests/platform/mac-wk2/TestExpectations:
* Source/WTF/Scripts/Preferences/UnifiedWebPreferences.yaml:

Canonical link: https://commits.webkit.org/303521@main

Author: jyavenard

LayoutTests/platform/mac-wk2/TestExpectations

@@ -2414,3 +2414,5 @@ webkit.org/b/302174 [ Tahoe Debug arm64 ] platform/mac/media/encrypted-media/fps
 # webkit.org/b/302674 fast/webgpu/nocrash/fuzz-279542.html appears to cause other tests to timeout
 [ Tahoe Debug arm64 ] fast/webgpu/nocrash/ [ Skip ]
 [ Tahoe Debug arm64 ] fast/selectors/is-backtracking.html [ Skip ]
+
+webkit.org/b/302935 [ Sonoma ] media/media-source/media-source-allowed-codecs.html [ Failure ]

Source/WTF/Scripts/Preferences/UnifiedWebPreferences.yaml

@@ -5357,7 +5357,7 @@ MediaSourcePrefersDecompressionSession:
 
 MediaSourceUseRemoteAudioVideoRenderer:
   type: bool
-  status: unstable
+  status: testable
   category: media
   humanReadableName: "MSE player uses GPU renderer"
   humanReadableDescription: "MSE player uses GPU renderer"