Stop testing on Dartium

pkgs/web_socket_channel/.travis.yml

diff --git a/pkgs/web_socket_channel/.travis.yml b/pkgs/web_socket_channel/.travis.yml
index a24a813..a6a7316 100644
--- a/pkgs/web_socket_channel/.travis.yml
+++ b/pkgs/web_socket_channel/.travis.yml
@@ -7,8 +7,6 @@
 dart_task:
   - test: --platform vm
   - test: --platform firefox -j 1
-  - test: --platform dartium
-    install_dartium: true
   - dartanalyzer
 
 matrix: