Update Documentation for New Environment Variable Definitions

[superbeeny]

What content needs to be created or modified?

Docs need to be updated to reflect changes in radius-project/design-notes#62

Describe the solution you'd like

Update examples in documentations to reflect new implementation

Where should the new material be placed?

Update existing documentation

The associated pull request from the Radius code repo, if applicable

radius-project/design-notes#62

Additional context

AB#13088

[superbeeny]

/assign

[ytimocin]

Thanks for the issue and the PR to fix this issue. Looking forward to reviewing it.