fix mi-cmd-stack.c

fix mi-cmd-stack.c

mi-cmd-stack.d had a conditional cleanup, "cleanup_tuple" that
confused the checker.  However, there was no need for this, since it
was only used via do_cleanups at the end of the function, just before
another call to do_cleanups.

So, while this is a stylistic patch for the checker, I also consider
it a generic improvement for readers of the code.

	* mi/mi-cmd-stack.c (list_arg_or_local): Remove
	"cleanup_tuple".