GDExtension: Fix `variant_iter_get()` actually calling `iter_next()`

(cherry picked from commit b14f359c941b9c16643e9cbbdda504802b4b440c)

core/extension/gdextension_interface.cpp

@@ -253,7 +253,7 @@ static void gdextension_variant_iter_get(GDExtensionConstVariantPtr p_self, GDEx
 	Variant *iter = (Variant *)r_iter;
 
 	bool valid;
-	memnew_placement(r_ret, Variant(self->iter_next(*iter, valid)));
+	memnew_placement(r_ret, Variant(self->iter_get(*iter, valid)));
 	*r_valid = valid;
 }