shill: cellular: Temporarily remove duplicate entries from provider database.

additional_providers.prototxt had duplicate entries for some providers from
serviceproviders.prototxt, to override the information.
This CL removes the old entries from serviceproviders.prototxt.

This is a stop-gap solution. Since serviceproviders.prototxt is a generated
database, we shouldn't update that database directly. A long term solution will
be posted to the same bug.

BUG=chromium:370194
TEST=Home Provider is correctly determined for e362.

Change-Id: Iccbc5a48ce52b4faa6fb100531001e9952abdce3
Reviewed-on: https://chromium-review.googlesource.com/198330
Commit-Queue: Prathmesh Prabhu <pprabhu@chromium.org>
Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>