Revert "updater_sample: add proguard.flags"

This reverts commit 8c3af4aa8c.

Reason for revert: Broke Master

Change-Id: I37bceeea630fb7db39efa25d03ababe3d84cdfbf

updater_sample/proguard.flags

@@ -1,23 +0,0 @@
-# Copyright (C) 2018 The Android Open Source Project
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-# Keep, used in tests.
--keep public class com.example.android.systemupdatersample.UpdateManager {
-   public int getUpdaterState();
-}
-
-# Keep, used in tests.
--keep public class com.example.android.systemupdatersample.UpdateConfig {
-   public <init>(java.lang.String, java.lang.String, int);
-}