[css-grid] Enable masonry feature flag

https://bugs.webkit.org/show_bug.cgi?id=247074
rdar://101595681

Reviewed by Tim Nguyen and Brent Fulgham.

Enable masonry by default on platforms.

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

Canonical link: https://commits.webkit.org/274661@main

Source/WTF/Scripts/Preferences/UnifiedWebPreferences.yaml

@@ -4300,17 +4300,17 @@ MaskWebGLStringsEnabled:
 
 MasonryEnabled:
   type: bool
-  status: preview
+  status: stable
   category: css
   humanReadableName: "CSS Masonry Layout"
   humanReadableDescription: "Enable Masonry Layout for CSS Grid"
   defaultValue:
     WebKitLegacy:
-      default: false
+      default: true
     WebKit:
-      default: false
+      default: true
     WebCore:
-      default: false
+      default: true
 
 MathMLEnabled:
   type: bool