todo: do a better job determining the third axis

[tlambert03]

this code is a lil' silly:

ndv/src/ndv/viewer/_viewer.py

Lines 341 to 347 in 7b6e48a

	# set the visibility of the last non-channel dimension
	sizes = list(self._data_wrapper.sizes())
	if self._channel_axis is not None:
	sizes = [x for x in sizes if x != self._channel_axis]
	if len(sizes) >= 3:
	dim3 = sizes[-3]
	self._dims_sliders.set_dimension_visible(dim3, True if ndim == 2 else False)