It's not possible to click the remove reviewer button.

Steps:
1. Go to Content / Content Structure.
2. Select content item.
3. Click Edit.
4. Click Send for Review.
5. Add a reviewer.
6. Try to remove the reviewer (screen attached).
Actual: Clicking on the "x" button has no effect.
Expected: It's possible to remove reviewer.

Remarks: Does not affect other browsers.