Minor errors in the 2nd part of our transport tutorial

[glatterf42]

While working on iiasa/ixmp4#108, I noticed a few minor error with the second part of our existing transport tutorial. It's probably not urgent to fix them since we are already re-implementing them in ixmp4.

https://github.com/iiasa/ixmp/blob/e12922f47227e0a9df25b2b76ccf5ef580bface8/tutorial/transport/py_transport_scenario.ipynb#L200-L201

The units here need to be "km", not "cases".

https://github.com/iiasa/ixmp/blob/e12922f47227e0a9df25b2b76ccf5ef580bface8/tutorial/transport/py_transport_scenario.ipynb#L18

There needs to be a newline before this one to render the list properly.