Update README_CN.md

Author: lizhuoyuan

README_CN.md

@@ -19,8 +19,8 @@
 [更新日志](https://github.com/OpenFlutter/flutter_screenutil/blob/master/CHANGELOG.md)
 
 ## Note
-[v3](https://github.com/OpenFlutter/flutter_screenutil/tree/beta)可用于`flutter> = 1.19.0`  
-[v2](https://github.com/OpenFlutter/flutter_screenutil)用于当前Flutter的`stable`版本。
+[v3](https://github.com/OpenFlutter/flutter_screenutil/tree/beta)可用于`flutter >= 1.19.0`  
+[v2](https://github.com/OpenFlutter/flutter_screenutil)可用于`flutter > 1.19.0`。
 
 ## 使用方法: