make uint benchmarks short，becauce can't pass github test.

neo.UnitTests/UT_UIntBenchmarks.cs

@@ -15,7 +15,7 @@ namespace Neo.UnitTests
     [TestClass]
     public class UT_UIntBenchmarks
     {
-        int MAX_TESTS = 1000000; // 1 million
+        int MAX_TESTS = 1000; // 1 million
 
         byte[][] base_32_1;
         byte[][] base_32_2;