Fix internal exception inheritance type.

Author: PatrykOlejniczak

UnitTest/DataStructuresTests/RedBlackTreeTest.cs

@@ -530,6 +530,6 @@ private static void CheckPathToEveryLeafHasSameNumberOfBlackNode(RedBlackTree<in
     /// <summary>
     ///     Exception class throw when any of red black tree rule is violation. Only for unit tests.
     /// </summary>
-    internal class RedBlackTreeViolationRuleException : ArgumentException
+    internal class RedBlackTreeViolationRuleException : Exception
     { }
 }