Fix win_powershell usings (#572)

Remove the unecessary using entry in the compiled code causing Roslyn to
emit a warning during compilation. This only affected people running
with an executable as the in process option did not need to recompile
the code that had this.

changelogs/fragments/win_powershell-fix-using.yml

@@ -0,0 +1,2 @@
+bugfixes:
+- win_powershell - Remove unecessary using in code causing stray error records in output - https://github.com/ansible-collections/ansible.windows/issues/571

plugins/modules/win_powershell.ps1

@@ -35,7 +35,6 @@ $module.Result.debug = @()
 $module.Result.information = @()
 
 $stdPinvoke = @'
-using Microsoft.Win32.SafeHandles;
 using System;
 using System.Runtime.InteropServices;