docs: fix readme node version (#7316)

Author: devwqc

README.md

@@ -7,7 +7,7 @@ This repo contains the source code and documentation powering [react.dev](https:
 ### Prerequisites
 
 1. Git
-1. Node: any 12.x version starting with v12.0.0 or greater
+1. Node: any version starting with v16.8.0 or greater
 1. Yarn: See [Yarn website for installation instructions](https://yarnpkg.com/lang/en/docs/install/)
 1. A fork of the repo (for any contributions)
 1. A clone of the [react.dev repo](https://github.com/reactjs/react.dev) on your local machine