Update .travis.yml for branch change (dart-lang/watcher#57)

pkgs/watcher/.travis.yml

diff --git a/pkgs/watcher/.travis.yml b/pkgs/watcher/.travis.yml
index c977430..2547644 100644
--- a/pkgs/watcher/.travis.yml
+++ b/pkgs/watcher/.travis.yml
@@ -8,7 +8,7 @@
 
 # Only building master means that we don't run two builds for each pull request.
 branches:
-  only: [master, 0.9.7+x]
+  only: [master]
 
 cache:
  directories: