Update documentation on binder proxy limit.

        private static final int MAIN_INDEX_SIZE = 1 <<  LOG_MAIN_INDEX_SIZE;

        private static final int MAIN_INDEX_MASK = MAIN_INDEX_SIZE - 1;

        /**

         * Debuggable builds will throw an BinderProxyMapSizeException if the number of

         * map entries exceeds:

         * We will throw a BinderProxyMapSizeException if the number of map entries

         * exceeds:

         */

        private static final int CRASH_AT_SIZE = 25_000;