Provide int to self._play_timer.setInterval

[nabobalis]

Description

I was trying to change the speed of the movie playback and saw this error:

TypeError: setInterval(self, msec: int): argument 1 has unexpected type 'float'
Traceback (most recent call last):
  File "/home/nabil/Git/glue/glue/utils/misc.py", line 55, in result
    return func(*args, **kwargs)
  File "/home/nabil/Git/glue-qt/glue_qt/viewers/common/data_slice_widget.py", line 163, in _adjust_play
    self._play_timer.setInterval(500 / abs(self._play_speed))
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I just now force this to be an int with the division.