docs: remove misleading upgrade notice from readme

[skip ci]

Author: gustavohenke

README.md

@@ -8,17 +8,11 @@
 An [express.js]( https://github.com/visionmedia/express ) middleware for
 [validator]( https://github.com/chriso/validator.js ).
 
-- [Upgrade notice](#upgrade-notice)
 - [Installation](#installation)
 - [Documentation](#documentation)
 - [Changelog](#changelog)
 - [License](#license)
 
-## Upgrade notice
-If you're arriving here as a express-validator v3 user after upgrading to v4+, please check the [upgrade guide](UPGRADE_GUIDE.md) in order to find out what's different!
-
-**Also please note that, starting with v5.0.0, no new features will be accepted into the legacy API. Only bug fixes will be made.**
-
 ## Installation
 ```
 npm install express-validator