Remove net/url_request/FailurePhase.java

This file was created manually during the first import process because
gn2bp did not support java_cpp_enum actions back then. This is now
supported in gn2bp, hence we don't need this file anymore.

See https://cs.android.com/android/platform/superproject/main/+/main:external/cronet/android/tools/gn2bp/gen_android_bp;l=1356?q=gn2bp&ss=android%2Fplatform%2Fsuperproject%2Fmain
for java_cpp_enum support.

Bug: 304217500
Change-Id: Ie37531fe0f7ca6850bc51b38a7dc90b9d844fc67

Author: Mohannad Farrag