Revert of Make DOMWrapperWorld::current() return a reference instead of a pointer

Source/bindings/tests/idls/TestImplements.idl

 /*
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 [
-    NoInterfaceObject, // Always used on target of 'implements'
+    NoInterfaceObject,  // Always used on target of 'implements'
 ] interface TestImplements {
     static readonly attribute long implementsStaticReadOnlyLongAttribute;
     static attribute DOMString implementsStaticStringAttribute;
     readonly attribute DOMString implementsReadonlyStringAttribute;
     attribute DOMString implementsStringAttribute;
     attribute Node implementsNodeAttribute;
     attribute EventHandler implementsEventHandlerAttribute;
 
     void implementsVoidMethod();
     [CallWith=ExecutionContext, RaisesException] TestInterfaceEmpty implementsComplexMethod(DOMString strArg, TestInterfaceEmpty testInterfaceEmptyArg);
     [Custom] void implementsCustomVoidMethod();
     static void implementsStaticVoidMethod();
 
     const unsigned short IMPLEMENTS_CONSTANT_1 = 1;
     [Reflect=IMPLEMENTS_REFLECT_CONSTANT] const unsigned short IMPLEMENTS_CONSTANT_2 = 2;
 
     [RuntimeEnabled=ImplementsFeatureName] attribute Node implementsRuntimeEnabledNodeAttribute;
     [PerContextEnabled=ImplementsContextName] attribute Node implementsPerContextEnabledNodeAttribute;
 };