fix test failure in CI of mgmt. packages (Azure#19829)

Author: tadelesh

eng/scripts/MgmtTestLib.ps1

@@ -22,7 +22,7 @@ function Invoke-MgmtTestgen ()
         [string]$config = "autorest.md",
         [string]$autorestVersion = "3.8.2",
         [string]$goExtension = "@autorest/go@4.0.0-preview.45",
-        [string]$testExtension = "@autorest/gotest@4.5.0",
+        [string]$testExtension = "@autorest/gotest@4.5.1",
         [string]$outputFolder
     )
     if ($clean)