Remove link leading to a 404 error in Deploy Keys page

### What does this MR do?

This MR removes a link that would lead an admin to believe he/she could edit a deploy key, but clicking on this link would lead to a 404.

### Screenshot

![image](https://gitlab.com/stanhu/gitlab-ce/uploads/b36cd76287d6389a09f9e0e49c1b6751/image.png)

### What are the relevant issue numbers?

Closes #1866

See merge request !923