Cover block: put "reset" option at the bottom of the list of replace options

[annezazu]

If you set media in a cover block and then open the "replace" flow, the reset option isn't at the bottom:

This feels unexpected and out of order. I'd expect it at the bottom.

[jsssun]

Hi!👋 I’d like to work on this

[annezazu]

I already have a PR underway @jsssun but I welcome you to help review it and contribute! Thanks for being interested.