Remove doc-only libraries from `setup_requires`

[vpipkt]

This one is up for debate.

We could possibly trim down the pyrasterframes setup_requires list by relying on the/a requirements.txt to define the dependencies for building docs. And carefully check that tests_require is correct. So, with the exception of pweave which we depend on in setup.py, the following are declared as setup_requires but really could be removed?

• rasterio: used in docs and test, but not required for running setup
• folium: only docs; we carefully avoid depending on it in rf_ipython; will enhance rendering of folium.Map if library is available
• boto3: suspect this is related to rasterio
• geopandas: test and docs only
• requests: docs only

On the one hand, removing dependencies not needed to install the package reduces friction.

On the other hand, making it less obvious how to get dependencies for docs build introduces friction.

The difference between the two hands is the size/orientation of community they represent.

Originally posted by @vpipkt in https://github.com/locationtech/rasterframes/pull/430