docs: update migration guide (#3811)

Author: snitin315

migration-v4.md

@@ -11,7 +11,7 @@ This document serves as a migration guide for `[email protected]`.
 ### ⚠ BREAKING CHANGES
 
 - Minimum supported `Node.js` version is `12.13.0`.
-- Minimum supported `webpack` version is `4.37.0` (**but we so recommend using 5 version**).
+- Minimum supported `webpack` version is `4.37.0` (**but we recommend using `webpack >= v5.0.0`**).
 - Minimum compatible `webpack-cli` version is `4.7.0`.
 - The `hotOnly` option was removed, if you need hot only mode, use `{ hot: 'only' }` value.