docs(contributing): keep documentation and engines in sync [ci skip]

Author: kuang-lingxi

.github/contributing.md

@@ -40,7 +40,7 @@ Hi! I'm really excited that you are interested in contributing to Vue.js. Before
 
 ## Development Setup
 
-You will need [Node.js](https://nodejs.org) **version 14+**, and [PNPM](https://pnpm.io).
+You will need [Node.js](https://nodejs.org) **version 16+**, and [PNPM](https://pnpm.io).
 
 We also recommend installing [ni](https://github.com/antfu/ni) to help switching between repos using different package managers. `ni` also provides the handy `nr` command which running npm scripts easier.