Update the avatar mask so it doesn’t cut off spaces’ avatars anymore (#8849)

* Update the avatar mask so it doesn’t cut off spaces’ avatars anymore
* Remove unused mask
* Remove unused class

Author: justjanne

res/css/structures/_UserMenu.scss

@@ -39,13 +39,6 @@ limitations under the License.
         margin-left: 10px;
     }
 
-    .mx_UserMenu_cutout .mx_BaseAvatar {
-        mask-image: url('$(res)/img/element-icons/roomlist/dnd-avatar-mask.svg');
-        mask-position: center;
-        mask-size: contain;
-        mask-repeat: no-repeat;
-    }
-
     .mx_UserMenu_dndBadge {
         position: absolute;
         bottom: -2px;