Fix appearance of participants menu button
Fix appearance of participants menu button

Buttons with icons should have a size of 44x44px for easier interaction.
This matches the height of the participant list item in which the button
appears, and as such also centers the button vertically with the name of
the participant.

With the larger size the default grey background of the button is now
much more visible, but as the button has no border the background looks
strange. Due to this the background is removed, which also gives the
menu button in the participant list a consistent look with the menu
button in the room list.

Signed-off-by: Daniel Calviño Sánchez <bd7629e975cc0e00ea7cda4ab6a120f2ee42ac1b@gmail.com>

nextcloud/spreed,nextcloud/spreed,nextcloud/spreed