Fix projects definitions

AdventOfCode2020/Day08.cs

@@ -1,6 +1,4 @@
-using System;
-using System.Collections.Generic;
-
+namespace AdventOfCode2020;
 
 /*
 
@@ -93,8 +91,6 @@ Fix the program so that it terminates normally by changing exactly one jmp (to n
 
 */
 
-namespace AdventOfCode2020;
-
 public class Day08 : IDay
 {
     public string ResolvePart1(string[] inputs)