Fix schema validation in Default Site

Should solve error `data/value must match exactly one schema in oneOf` when setting the Default Site to 404 or 444. #4074

backend/schema/components/setting-object.json

@@ -25,7 +25,7 @@
 		"value": {
 			"description": "Value in almost any form",
 			"example": "congratulations",
-			"oneOf": [
+			"anyOf": [
 				{
 					"type": "string",
 					"minLength": 1