dialer-button: Fix emitting signal

As the properties where set to not explicitly fire ::notify, no
signals where emitted. Let it be not explicit so that
the signal will be emitted on change
1 job for wip/sadiq/fixes in 2 minutes and 3 seconds (queued for 1 minute)
Status Job ID Name Coverage
  Build
passed #2072
librem5
build-debian

00:02:03