GDScript: Don't use validated call for vararg methods

Since they may have runtime type validation, we cannot use the validated
call.

modules/gdscript/tests/scripts/analyzer/warnings/lambda_unused_arg.gd

@@ -1,4 +1,4 @@
 func test():
 	var lambda := func(unused: Variant) -> void:
 		pass
-	lambda.call()
+	lambda.call("something")