SystemUI: fix size of icon of vibrate ringer mode

Vibrate ringer mode icon uses 19dp height and width while
all other ringer modes use 24dp. This leads to inconsistent
and ugly vibrate icon in volume panel.

Change-Id: I8733aef4e9a68fe994815e5c8d92afe60f48f704
Signed-off-by: Jesse Chan <jc@lineageos.org>