Commiting a trivial README.md change for the Firefox sheriffs to test…

… backout.

README.md

@@ -2,7 +2,7 @@
 
 [![Linux Build Status](https://img.shields.io/travis/servo/servo/master.svg?label=Linux%20build)](https://travis-ci.org/servo/servo)  [![Windows Build Status](https://img.shields.io/appveyor/ci/servo/servo/master.svg?label=Windows%20build)](https://ci.appveyor.com/project/servo/servo/branch/master)  [![Changelog #228](https://img.shields.io/badge/changelog-%23228-9E978E.svg)](https://changelog.com/podcast/228)
 
-Servo is a prototype web browser engine written in the
+Servo is a web browser engine written in the
 [Rust](https://github.com/rust-lang/rust) language. It is currently developed on
 64bit OS X, 64bit Linux, and Android.