Removed extra time in test

Dart 2.1 has been released which fixes the problem with this test:
dart-lang/sdk#34090

Author: julemand101

test/day13_test.dart

@@ -1,9 +1,6 @@
 // --- Day 13: Packet Scanners ---
 // https://adventofcode.com/2017/day/13
 
-// Need more time because Travis are a little slow
-@Timeout(const Duration(minutes: 5))
-
 import 'dart:io';
 import 'package:test/test.dart';
 import 'package:AdventOfCode2017/day13.dart';