Get rid of all the library tags.

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1582503003 .

lib/source_map_stack_trace.dart

diff --git a/lib/source_map_stack_trace.dart b/lib/source_map_stack_trace.dart
index 893135f..23aed77 100644
--- a/lib/source_map_stack_trace.dart
+++ b/lib/source_map_stack_trace.dart
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-library source_map_stack_trace;
-
 import 'package:path/path.dart' as p;
 import 'package:source_maps/source_maps.dart';
 import 'package:stack_trace/stack_trace.dart';