The help content for "Get-Help powershell.exe" needs to be updated to reflect the new name 'pwsh' #5181

Running get-help pwsh.exe fails now, while running get-help powershell.exe prints the old help content for powershell.exe.

Two things need to be done to update the help content:

1. The local help content we pull in during build needs to be updated. We pull in using the nuget package powershellhelpfiles, and the help content are packed in that nuget package.
2. The online help content needs to be udpated.