LibWeb: Skip DedicatedWorkerGlobalScope-instanceof test

It is consistently hanging on mac. See #1306 for details.

(cherry picked from commit feaf2feab8fbd855f526a5a4eec2395fdec6a749)

Tests/LibWeb/TestConfig.ini

@@ -1,15 +1,16 @@
 [Skipped]
-Text/input/HTML/cross-origin-window-properties.html
+Ref/css-keyframe-fill-forwards.html
+Ref/unicode-range.html
 Text/input/Crypto/SubtleCrypto-exportKey.html
 Text/input/Crypto/SubtleCrypto-generateKey.html
+Text/input/HTML/cross-origin-window-properties.html
+Text/input/HTML/DedicatedWorkerGlobalScope-instanceof.html
 Text/input/WebAnimations/misc/DocumentTimeline.html
+Text/input/window-scrollTo.html
 Text/input/Worker/Worker-blob.html
 Text/input/Worker/Worker-crypto.html
 Text/input/Worker/Worker-echo.html
 Text/input/Worker/Worker-importScripts.html
 Text/input/Worker/Worker-location.html
 Text/input/Worker/Worker-module.html
 Text/input/Worker/Worker-performance.html
-Text/input/window-scrollTo.html
-Ref/unicode-range.html
-Ref/css-keyframe-fill-forwards.html