Just one line that we should remove.

https://codereview.chromium.org/2635193002 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fa5c0f2b9380b8a93c72b5ccde08b82203fbc5b0

commit fa5c0f2b9380b8a93c72b5ccde08b82203fbc5b0
Author: pauljensen <pauljensen@chromium.org>
Date: Tue Jan 17 14:46:40 2017

[Cronet] Remove useless proguard line referencing deleted old API

This is no longer needed and should be removed.

R=xunjieli
BUG= 678933 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_cronet_tester

Review-Url: https://codereview.chromium.org/2635193002
Cr-Commit-Position: refs/heads/master@{#444049}

[modify] https://crrev.com/fa5c0f2b9380b8a93c72b5ccde08b82203fbc5b0/components/cronet/android/cronet_impl_native_proguard.cfg