Move to PS7

Author: adityapatwardhan

.ci/test.yml

@@ -133,6 +133,7 @@ jobs:
       MAPPED_ADO_PRIVATE_REPO_URL: $(ado_private_repo_url)
     displayName: 'Execute functional tests with AzAuth'
     condition: eq(${{ parameters.useAzAuth }}, true)
+    pwsh: true
 
   - ${{ parameters.powershellExecutable }}: |
       $modulePath = Join-Path -Path $env:AGENT_TEMPDIRECTORY -ChildPath 'TempModules'