swaync-fbcli: migrate an "echo" to a "log"

hosts/common/programs/swaynotificationcenter/swaync-fbcli

@@ -13,7 +13,7 @@ log() {
 
 # kill children if killed, to allow that killing this parent process will end the real fbcli call
 cleanup() {
-  echo "aborting fbcli notification (PID $child)"
+  log "aborting fbcli notification (PID $child)"
   pkill -P "$child"
   exit 0  # exit cleanly to avoid swaync alerting a script failure
 }