Removed supported Play version from README

The plug-in definitely supports both Play 2.4 and Play 2.3.  So let's remove the note about supported versions as it's more confusing than useful.

README.md

@@ -4,10 +4,6 @@ This is an extension to Scala IDE to support Play 2.x routes and template files.
 
 For user documentation, check the [wiki](https://github.com/scala-ide/scala-ide-play2/wiki).
 
-# Supported Play versions
-
-This plugin provides Eclipse supports for Play 2.3.x projects. However, it should also work with older Play releases.
-
 ## Project structure
 
 The project is composed of 5 Eclipse plugins: