Remove an unused dependency on collection.

pkgs/watcher/pubspec.yaml

diff --git a/pkgs/watcher/pubspec.yaml b/pkgs/watcher/pubspec.yaml
index bee3546..90f96f5 100644
--- a/pkgs/watcher/pubspec.yaml
+++ b/pkgs/watcher/pubspec.yaml
@@ -1,5 +1,5 @@
 name: watcher
-version: 0.9.7+3
+version: 0.9.8-dev
 author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/dart-lang/watcher
 description: >
@@ -9,7 +9,6 @@
   sdk: '>=1.9.0 <2.0.0'
 dependencies:
   async: '^1.10.0'
-  collection: '^1.0.0'
   path: '>=0.9.0 <2.0.0'
 dev_dependencies:
   benchmark_harness: '^1.0.4'