actuator panel: fix type errors

[kand198]

This PR fixes two type errors in the actuator panel.

Bugs caused by these errors:

• Changes to the broadcast interval input do not change the broadcast interval timer's interval value.
• Changing command value directly in the command value spinbox does not update the corresponding command value slider component.
• When changing the broadcast interval input, command value spinbox, or command value slider, a large number of errors are emitted, spamming the output.

Traceback samples:

Broadcast interval:

Traceback (most recent call last):
  File "C:\Users\keith.anderson\git\gui_tool\dronecan_gui_tool\panels\actuator_panel.py", line 138, in <lambda>
    lambda: self._bcast_timer.setInterval(self._bcast_interval.value() * 1e3))
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: setInterval(self, msec: int): argument 1 has unexpected type 'float'

Slider:

Traceback (most recent call last):
  File "C:\Users\keith.anderson\git\gui_tool\dronecan_gui_tool\panels\actuator_panel.py", line 49, in <lambda>
    self._spinbox.valueChanged.connect(lambda: self._slider.setValue(self._spinbox.value()*1000.0))
                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: setValue(self, a0: int): argument 1 has unexpected type 'float'

[joshanne]

Thanks @kand198 - I actually ran into this a few days ago too and was about to fix it! LGTM.