fdo#55903 - fixed zoom mode button tooltip for better understanding

Change-Id: I42c5ad557c00d2db80e691332756a544651ab7de
Reviewed-on: https://gerrit.libreoffice.org/11596
Reviewed-by: Maxim Monastirsky <momonasmon@gmail.com>
Tested-by: Maxim Monastirsky <momonasmon@gmail.com>