Merge pull request #1633 from PowerShell/revert_psedition_namechange

Revert the changes made in #1457. Desktop and Core are the PowerShell Edition names. Remove Linux as edition name.

test/powershell/Host/PSVersionTable.Tests.ps1

@@ -20,6 +20,6 @@ Describe "PSVersionTable" -Tags "CI" {
     }
 
     It "Should have the correct edition" -Skip:(!$IsCoreCLR) {
-	$PSVersionTable["PSEdition"] | Should Be "PowerShellCore"
+	$PSVersionTable["PSEdition"] | Should Be "Core"
     }
 }