Inconsistent avatar sizes and gaps in approvals section of MR widget

The approvals section of the MR widget has some inconsitent avatar sizes and spacing and lacks tooltips for all user avatars.

Proposal

1. All user avatars in the approvals sections should be 24px in width and height with 8px space between them.
2. The space between the status text and the avatar should be 8px (since they are related)
3. The space between the avatars and the "Remove your approval" button should be 16px
4. All user avatars should have a tooltip to display the user's name.