The difference is that the first is in the past tense (You hid) and the second is in the present perfect (You have hidden). Neither is incorrect and both mean essentially the same thing.
There are two differences: one is that the past implies a one-time action in the past, whereas the present perfect can refer to a more continuous action in the past. See this tenses chart for a temporal diagram. However, since in this context there is only one possible way to hide a request (you did it one time, not continuously), it means the same thing either way.
The second difference is, as pointed out in the first comment below, that the present perfect "implies that the action still relates to the present". When you say "You hid a request", it sounds like history (not relevant to your immediate situation); but when you say "You have hidden a request", it sounds as if either you just did it, or that you are going to need to make a decision about that past action.