[windows] Update plugin template (#64521)

The pointer-argument-based version of Success() is deprecated; this
updates the template to use the new reference-based version (which
allows for inline construction of the response value).

Part of https://github.com/flutter/flutter/issues/63975

packages/flutter_tools/templates/plugin/windows.tmpl/projectName_plugin.cpp.tmpl

@@ -72,8 +72,7 @@ void {{pluginClass}}::HandleMethodCall(
     } else if (IsWindows7OrGreater()) {
       version_stream << "7";
     }
-    flutter::EncodableValue response(version_stream.str());
-    result->Success(&response);
+    result->Success(flutter::EncodableValue(version_stream.str()));
   } else {
     result->NotImplemented();
   }