fix PowerShell#1393: Always use local help to return Full help

If the user has overridden the Get-Help -Online parameter to always be true, then the ShowHelpHandler will always launch a new browser window to the cmdlet help.
Instead, we want it to return the full cmdlet text as intended.

Author: deadlydog

src/PowerShellEditorServices/Services/PowerShellContext/Handlers/ShowHelpHandler.cs

@@ -62,7 +62,7 @@ public async Task<Unit> Handle(ShowHelpParams request, CancellationToken cancell
                     [System.Net.ServicePointManager]::SecurityProtocol = $oldSslVersion
                 }
 
-                return Microsoft.PowerShell.Core\Get-Help $CommandName -Full
+                return Microsoft.PowerShell.Core\Get-Help $CommandName -Full -Online:$false
                 ";
 
             string helpParams = request.Text;