avm2: stub xml.normalize() (#10709)

* avm2: stub xml.normalize()

core/src/avm2/globals/XML.as

@@ -4,6 +4,11 @@ package {
     public final dynamic class XML {
         import __ruffle__.stub_method;
 
+        AS3 function normalize(): XML {
+            stub_method("XML", "normalize");
+            return this;
+        }
+        
         AS3 static function setSettings(settings:Object): void {
             stub_method("XML", "setSettings");
         }
@@ -135,5 +140,10 @@ package {
             var self:XML = this;
             return self.AS3::text();
         };
+        
+        prototype.normalize = function():XML {
+            var self:XML = this;
+            return self.AS3::normalize();
+        };
     }
 }