remove sauce access key in travis.yml

Author: tinayuangao

.travis.yml

@@ -18,7 +18,6 @@ env:
   global:
   - LOGS_DIR=/tmp/angular-material2-build/logs
   - SAUCE_USERNAME=angular-ci
-  - SAUCE_ACCESS_KEY=9b988f434ff8-fbca-8aa4-4ae3-35442987
   - BROWSER_STACK_USERNAME=angularteam1
   - BROWSER_STACK_ACCESS_KEY=BWCd4SynLzdDcv8xtzsB
   - BROWSER_PROVIDER_READY_FILE=/tmp/angular-material2-build/readyfile