Revert change made that tried to write to a property

Author: philipstarkey

labscript/core.py

@@ -73,9 +73,10 @@ def add_device(self, device):
             self._clock_limit = device.clock_limit
         # Update minimum clock high time if this new device requires a longer high time.
         if getattr(device, 'minimum_clock_high_time', None) is not None:
-            self.minimum_clock_high_time = max(
+            self._minimum_clock_high_time = max(
                 device.minimum_clock_high_time, self.minimum_clock_high_time
             )
+
     @property
     def clock_limit(self):
         """float: Clock limit for this line, typically set by speed of child Intermediate Devices."""