Absolute move fails

Absolute moves (calling /actions/stage/move with absolute=true) fail with error

TypeError: int() argument must be a string, a bytes-like object or a number, not 'generator'

The solution is to add a tuple to the relevant line of openflexure_microscope/api/v2/actions/stage.py. It's a one-line fix but I'm on the wrong branch to make a MR.