Delete unused targets in //third_party/proguard/BUILD.gn

Bug: None
Change-Id: I352d059ef8d4103cf0ceb4a742cbeceda1c85c9c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2212475
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Sam Maier <smaier@chromium.org>
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Sam Maier <smaier@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771565}

third_party/proguard/BUILD.gn

-# Copyright 2017 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-import("//build/config/android/rules.gni")
-
-# This target is used only by retrace. proguard.jar (v5.2.1) is used for
-# compiling, and is reference directly via "java -jar proguar.jar"
-java_prebuilt("proguard603_java") {
-  jar_path = "lib/proguard603.jar"
-  data = [ "$root_build_dir/lib.java/third_party/proguard/proguard603.jar" ]
-}
-
-java_prebuilt("retrace_java") {
-  jar_path = "lib/retrace603.jar"
-  deps = [ ":proguard603_java" ]
-  data = [ "$root_build_dir/lib.java/third_party/proguard/retrace603.jar" ]
-}