Fix doctest failing due to change in 'netcdf_promote' future behaviour

Author: djkirkham

docs/iris/src/userguide/regridding_plots/interpolate_column.py

@@ -10,7 +10,7 @@
 
 
 fname = iris.sample_data_path('hybrid_height.nc')
-column = iris.load_cube(fname)[:, 0, 0]
+column = iris.load_cube(fname, 'air_potential_temperature')[:, 0, 0]
 
 alt_coord = column.coord('altitude')