ID 394511 - Edit the environment variable documentation to include MARI_PLUGINS_PATH

Problem summary

Add the MARI_PLUGINS_PATH environment variable to the Environment Variables That Mari Recognizes documentation here

Customer reported version

Customer reported platform

Steps to reproduce

1) Open this link

2) Look through the documented environment variables

result: MARI_PLUGINS_PATH is not there

Expected behaviour
MARI_PLUGINS_PATH to be included 

Actual behaviour

MARI_PLUGINS_PATH is not included

Workaround

Reproduced by support
This bug has been reproduced in here:

https://learn.foundry.com/mari/Content/user_guide/extending_mari/environment_variables.html