都是对的.区别是：
1 time limited --------强调“时间有限,已经被规定了数量”
比如说：
We can't finish our work within the limited time given.
--------比如说,所规定的时间是a week.
== We can't finish our work within a week.
2 time limiting + 宾语
比如说：
Time limiting us,we have to finish the work in a week.
--------这里的time limiting us是独立主格结构,强调原因,变成句子就是：As time limits us.