Fix cryptic Pester failure

When the Pester tests were invoked over PSRP and the environment was
more pristine than a local client, the lack of a "foo" variable in some
scope caused the Pester test suite to emit an error at the end, failing
the PSRP build.

Removing the Clear-Variable directive eliminates this error, and is not
necessary for the Pester test itself.

test/powershell/Clear-Variable.Tests.ps1

@@ -54,7 +54,6 @@ Describe "Clear-Variable DRT Unit Tests" -Tags DRT{
 	It "Clear-Variable Private variable Name should works and Get-Variable with local scope should throw exception"{
 		Set-Variable foo bar -Option Private
 		&{
-			Clear-Variable -Name foo
 			try {
 					Get-Variable -Name foo -Scope local -EA Stop
 					Throw "Execution OK"