use constructor default tempo when instantiating Link

Author: giohappy

isobar/timelines/clock_link.py

@@ -16,7 +16,7 @@ def __init__(self,
                  clock_target: Any = None,
                  tempo: float = DEFAULT_TEMPO,
                  ticks_per_beat: int = DEFAULT_TICKS_PER_BEAT):
-        self.link_client = link.Link(120)
+        self.link_client = link.Link(tempo)
         self.link_client.enabled = True
         self.link_client.startStopSyncEnabled = True
         self.link_client.setTempoCallback(self.tempo_changed_callback)