Revert "Android: Fix cronet proguard failure when enable_chrome_android_internal=true"

This reverts commit 06e0fcb1.

Reason for revert: No longer necessary.

Original change's description:
> Android: Fix cronet proguard failure when enable_chrome_android_internal=true
>
> Tested that all targets now build via:
> autoninja -C out/Release $(build/android/list_java_targets.py --proguard-enabled)
>
> Bug: 1155547
> Change-Id: Ie32d62e108778c219a190e363be9c82b747a2a02
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2574597
> Auto-Submit: Andrew Grieve <agrieve@chromium.org>
> Commit-Queue: Paul Jensen <pauljensen@chromium.org>
> Reviewed-by: Paul Jensen <pauljensen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#833824}

TBR=pauljensen@chromium.org,agrieve@chromium.org,chromium-scoped@luci-project-accounts.iam.gserviceaccount.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1155547
Change-Id: I0361ac731d01e97012e21547201969cb3a492cd6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2593769Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Paul Jensen <pauljensen@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837135}

components/cronet/android/test/proguard.cfg

@@ -11,9 +11,6 @@
 # https://android.googlesource.com/platform/sdk/+/marshmallow-mr1-release/files/proguard-android.txt#54
 -dontwarn android.support.**
 
-# Temporary fix for https://bugs.chromium.org/p/chromium/issues/detail?id=1155547
--dontwarn com.google.protobuf.**
-
 # Do not obfuscate this class for testing since some of the tests check the class
 # name in order to check that an instantiated engine is the Java one.
 -keepnames class org.chromium.net.impl.JavaCronetEngine