[Feature Request]: Remove the latest PowerShell installation from the `Set-EnvironmentOnAgent` script once the MS-hosted agents have been updated to PSVersion 7.3.0

### Description

Remove the latest PowerShell installation from the [`Set-EnvironmentOnAgent`](https://github.com/Azure/ResourceModules/blob/main/utilities/pipelines/sharedScripts/Set-EnvironmentOnAgent.ps1) script once the MS-hosted agents have been updated to PSVersion 7.3.0.