Linux installation documentation does not provide instructions on how to update environment after git pull

[Perryman]

Describe the bug
Linux documentation

To Reproduce
Steps to reproduce the behavior:

1. Go to 'INSTALL_LINUX.md#updating-to-newer-versions-of-the-script'
2. Necessary instructions are not provided to update the environment, if required.

Expected behavior
A section below that provides the proper commands to update the environment after running git pull