Outdated Installation Instruction docs

The installation instructions for bilby_pipe at:

https://lscsoft.docs.ligo.org/bilby_pipe/master/installation.html

are out of date. Specifically:

bilby_pipe is developed and tested for Python 3.6, and 3.7. In the following, we demonstrate how to install a development version of bilby_pipe on a LIGO Data Grid (LDG) cluster.

and

For detailed help on creating and managing environments see these help pages. Here is an example of creating and activating an environment named bilby

conda create -n bilby python=3.7

conda activate bilby

It advises to use bilby_pipe with Python 3.7, while the 1.0.6 version of bilby_pipe is no longer compatible with this version of Python.