LibWeb: Use "valid-types" to define `fill-rule` in Properties.json

No behaviour change.

Userland/Libraries/LibWeb/CSS/Properties.json

@@ -864,10 +864,7 @@
     "animation-type": "discrete",
     "inherited": true,
     "initial": "nonzero",
-    "valid-identifiers": [
-      "nonzero",
-      "evenodd"
-    ]
+    "valid-types": [ "fill-rule" ]
   },
   "flex": {
     "inherited": false,