Remove weborigin rules from DEPS as weborigin/ was fold back under platform/. 

This is follow-up to https://codereview.chromium.org/54053006.

BUG=307407

TBR=ch.dumez@samsung.com

Review URL: https://codereview.chromium.org/109863002

git-svn-id: svn://svn.chromium.org/blink/trunk@163394 bbb929c8-8fbe-4397-9dbb-9b2b20218538