Update DynamicNumber.cs

Author: mythz

src/ServiceStack.Text/DynamicNumber.cs

@@ -642,7 +642,7 @@ public static IDynamicNumber AssertNumbers(string name, object lhs, object rhs)
         public static object Log(object lhs, object rhs) => AssertNumbers(nameof(Log), lhs, rhs).log(lhs, rhs);
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static object CompareTo(object lhs, object rhs) => AssertNumbers(nameof(CompareTo), lhs, rhs).compareTo(lhs, rhs);
+        public static int CompareTo(object lhs, object rhs) => AssertNumbers(nameof(CompareTo), lhs, rhs).compareTo(lhs, rhs);
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static object BitwiseAnd(object lhs, object rhs) => AssertNumbers(nameof(BitwiseAnd), lhs, rhs).bitwiseAnd(lhs, rhs);