Fix string conversion of Microsoft.TestPlatform.Extensions.TrxLogger.ObjectMode.TestOutcome (#4243) (#4246)

Fix string conversion of `Microsoft.TestPlatform.Extensions.TrxLogger.ObjectMode.TestOutcome`

Author: MarcoRossignoli

src/Microsoft.TestPlatform.Extensions.TrxLogger/ObjectModel/TestOutcome.cs

@@ -86,15 +86,5 @@ internal enum TestOutcome
     /// <summary>
     /// Test is in the execution queue, was not started yet.
     /// </summary>
-    Pending,
-
-    /// <summary>
-    /// The min value of this enum
-    /// </summary>
-    Min = Error,
-
-    /// <summary>
-    /// The max value of this enum
-    /// </summary>
-    Max = Pending
+    Pending
 }