Intake-ESM Catalog include a column of 'long_name' instead of 'variable_long_name'

In `using-intake-catalog.ipynb`, the catalog returned only includes a column `long_name` rather than `variable_long_name`, which was referenced in the code many times and will result in runtime error. 

If there is a change in the catalog after this notebook was written, I can draft a PR to change all the occurrences of `variable_long_name` to `long_name`.  