Change pyuvdata future array shapes check

[jburba]

This is a currently inconsequential error, but the boolean attribute should be uvd.future_array_shapes as opposed to what's currently used, uvd.use_future_array_shapes which is a function. Right now, the frequency array freqs is unused except for it's size, so the shape doesn't matter. We should change the calls to uvd.use_future_array_shapes in case this matters in the future, though.

See e.g. line 309 in run-hydra-pspec.py.