Docs needed for 'Add Environment Variable override of telemetry'

[joeyaiello]

This issue was generated because an issue in the
PowerShell/PowerShell repository had an issue marked
as Documentation Needed and should instead be tracked here in PowerShell-Docs.

The pull request or issue that contains this is located at PowerShell/PowerShell#6063

[matt9ucci]

@sdwheeler The issue is already resolved by #2111

[sdwheeler]

@matt9ucci Thanks