refactor: deprecate app indexing (#1334)

* deprecate app indexing

* remove app indexing from ci build script

Author: thatfiredev

app-indexing/README.md

@@ -1,48 +1,7 @@
 Firebase App Indexing Quickstart
 ==============================
 
-The Firebase App Indexing Android quickstart demonstrates how to get your app to be found in Google Search.
+Firebase App Indexing is no longer the recommended way of indexing content for display as suggested results in Google Search App.
 
-Introduction
-------------
+Please check the [App Indexing Documentation](https://firebase.google.com/docs/app-indexing) for more details.
 
-- [Read more about Firebase App Indexing](https://firebase.google.com/docs/app-indexing/)
-
-Getting Started
----------------
-
-- [Add Firebase to your Android Project](https://firebase.google.com/docs/android/setup).
-- Open the App Indexing project in Android Studio.
-- Run the sample on your Android device or emulator by issuing the following command using **adb** tool:  
-`adb shell am start -a android.intent.action.VIEW -d "https://www.example.com/articles/test" com.google.samples.quickstart.appindexing`
-- Use ADD STICKERS and CLEAR STICKERS buttons to add and remove stickers from the index.
-
-Result
------------
-<img src="app/src/screen.png" height="534" width="300"/>
-
-Support
--------
-
-- [Stack Overflow](https://stackoverflow.com/questions/tagged/android-app-indexing)
-- [Firebase Support](https://firebase.google.com/support/)
-
-License
--------
-
-Copyright 2018 Google, Inc.
-
-Licensed to the Apache Software Foundation (ASF) under one or more contributor
-license agreements.  See the NOTICE file distributed with this work for
-additional information regarding copyright ownership.  The ASF licenses this
-file to you 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.