Add detail to error message that Disconnect is only supported with WSMan

[SteveL-MSFT]

PR Summary

If you use Disconnect-PSSession with a PSSession using any transport other than WSMan, the error message doesn't give enough details why it failed. Fix is to specify that this capability is only supported with WSMan.

Fix #5313

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Change is not breaking
• Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
• This PR is ready to merge and is not Work in Progress.
  • If the PR is work in progress, please add the prefix WIP: to the beginning of the title and remove the prefix when the PR is ready.
• User-facing changes
  • Not Applicable
  • OR
  • User-facing clarify that disconnect only works with WSMan MicrosoftDocs/PowerShell-Docs#2344
    • Issue filed - Issue link:
• Testing - New and feature
  • Not Applicable or can only be tested interactively
  • OR
  • Make sure you've added a new test if existing tests do not effectively test the code changed
    • Add [feature] if the change is significant or affects feature tests

[iSazonov]

From the message I understand nothing that I should do.
Maybe simply say "The disconnection operation is not supported for SSH sessions."

[SteveL-MSFT]

It's also not supported for named pipes and PowerShell Direct remoting. The doc update I linked in the PR description should hopefully make this more clear.

[iSazonov]

@SteveL-MSFT Is the PR really fix #5313? Maybe not close the Issue?

[SteveL-MSFT]

@iSazonov there's no immediate plan to support Connect/Disconnect with anything other than WSMan. I've submitted some doc updates to reflect this. Longer term, we will want to support this scenario. However, on Linux/macOS, you would use screen which isn't available on Windows. I think it's fine to close this issue as we'll have to revisit the SSH remoting hosting problem when we try to enable JEA for SSH remoting.