Remove sdch mention from src/DEPS

TBR=rdsmith@chromium.org

Bug: 762686
Change-Id: I644d345d283528b417a5a8398bf40530a8ace1f7
Reviewed-on: https://chromium-review.googlesource.com/673095Reviewed-by: Helen Li <xunjieli@chromium.org>
Reviewed-by: Randy Smith <rdsmith@chromium.org>
Commit-Queue: Helen Li <xunjieli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502930}

DEPS

@@ -535,7 +535,6 @@ skip_child_includes = [
   'breakpad',
   'native_client_sdk',
   'out',
-  'sdch',
   'skia',
   'testing',
   'v8',