Remove AndroidHttpClient class after Roboelectric update

briar-android/src/test/java/android/net/http/AndroidHttpClient.java

-package android.net.http;
-
-// This class is here to fix an issue with Robolectric.
-// https://github.com/robolectric/robolectric/issues/1862
-// TODO: Check if this class can be removed on next Robolectric update
-public class AndroidHttpClient {
-}
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