Turn on constructible & adoptable CSSStyleSheet objects

https://bugs.webkit.org/show_bug.cgi?id=245931

Reviewed by Darin Adler.

Turn on constructible & adoptable CSSStyleSheet objects now that it is fully
implemented and passes most WPT tests.

* Source/WTF/Scripts/Preferences/WebPreferencesExperimental.yaml:

Canonical link: https://commits.webkit.org/255067@main

Source/WTF/Scripts/Preferences/WebPreferencesExperimental.yaml

@@ -525,11 +525,11 @@ ConstructableStylesheetsEnabled:
   humanReadableDescription: "Enable Constructable Stylesheets"
   defaultValue:
     WebKitLegacy:
-      default: false
+      default: true
     WebKit:
-      default: false
+      default: true
     WebCore:
-      default: false
+      default: true
 
 ContactPickerAPIEnabled:
   type: bool