Remove some description (#946)

* Update README.md

* Update README_ZH.md

README.md

@@ -15,7 +15,7 @@ Underlying technology is a distributed tracing system.
 [![OpenTracing-1.x Badge](https://img.shields.io/badge/OpenTracing--1.x-enabled-blue.svg)](http://opentracing.io)
 
 * Provide Java agent, **no need to CHANGE any application source code**.
-  * High performance agent. Only increase extra **10%** cpu cost in 5000+ tps application, even **when collect all traces**.
+  * High performance agent. 
   * [Supported middlewares, frameworks and libraries](docs/Supported-list.md).
 * Manual instrumentation
   * As an [OpenTracing supported tracer](http://opentracing.io/documentation/pages/supported-tracers)

README_ZH.md

@@ -15,7 +15,7 @@ Apache SkyWalking | [English](README.md)
 
 
 * Java自动探针，**不需要修改应用程序源代码**
-  * 高性能探针，针对单实例5000tps的应用，在**全量采集的情况下**，只增加 **10%** 的CPU开销。
+  * 高性能探针.
   * [中间件，框架与类库支持列表](docs/Supported-list.md).
 * 手动探针
   * [使用OpenTracing手动探针API](http://opentracing.io/documentation/pages/supported-tracers)