Remove drop('x') from add_s_alpha_geometry_coords()

The index-value coordinates are now added for dimensions without
coordinates after the geometry is applied, so no 'x' coordinate has been
created to drop.

xbout/geometries.py

@@ -292,8 +292,6 @@ def add_s_alpha_geometry_coords(ds, *, coordinates=None, grid=None):
                          "geometry='s-alpha'")
     ds['r'] = ds['hthe'].isel({ycoord: 0}).squeeze(drop=True)
     ds['r'].attrs['units'] = 'm'
-    # remove x-index coordinate, don't need when we have 'r' as a radial coordinate
-    ds = ds.drop('x')
     ds = ds.set_coords('r')
     ds = ds.rename(x='r')
     ds.metadata['bout_xdim'] = 'r'