Update test to construct the version from $PSVersionTable.PSVersion - #5557

Describing Validate Register-PSSessionConfiguration, Set-PSSessionConfiguration cmdlets
   Context Validate Register-PSSessionConfiguration
    [-] Validate Register-PSSessionConfiguration -name -path 14.51s
      Expected: {6}
      But was:  {6.1}
      at line: 491 in C:\projects\powershell-f975h\test\powershell\Modules\Microsoft.PowerShell.Core\PSSessionConfiguration.Tests.ps1
      491:                     $Result.Session.PSVersion | Should be 6.0
   Context Validate Set-PSSessionConfiguration
    [-] Validate Set-PSSessionConfiguration -name -path -MaximumReceivedObjectSizeMB -MaximumReceivedDataSizePerCommandMB -UseSharedProcess -ThreadOptions parameters 27.69s
      Expected: {6}
      But was:  {6.1}
      at line: 560 in C:\projects\powershell-f975h\test\powershell\Modules\Microsoft.PowerShell.Core\PSSessionConfiguration.Tests.ps1
      560:                     $Result.Session.PSVersion | Should be 6.0