Make sure to drop coordinates before renaming and reassigning
Make sure to drop coordinates before renaming and reassigning

When combining TOVSCollocatedDataset with additional data from FCDR, I
need to reassign dimensions.  Starting with xarray 0.10, xarray enforces
to not rename dimensions if their coordinates don't match.  Explicitly
drop the coordinates before renaming the dimensions and assigning new
coordinates.

atmtools/typhon,atmtools/typhon