update notebooks to make use of earthaccess for authentication

[Mikejmnez]

Delegating authentication to earthaccess makes things much easier since:

• GettingStarted.ipynb notebook would not be necessary.
• Any notebook can be run at any order.

One can motivate the use of a .netrc to store local credentials, but for interactive purposes, it is nice to have earthaccess authenticate EDL username/password, and it provides pydap with the token bearer.