Fix assignment of PSDefaultParameterValues

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Author: adityapatwardhan

test/DscResource/PSResourceGetDSCResource.Tests.ps1

@@ -115,7 +115,7 @@ Describe 'Repository Resource Tests' -Tags 'CI' {
     }
     AfterAll {
         if ($skipTest) {
-            $PSDefaultParameterValues = $originalDefaultParameterValues
+            $global:PSDefaultParameterValues = $originalDefaultParameterValues
             return
         }