docs(migrate): update usage info (webpack#4954)

Author: jamesgeorge007

src/content/migrate/5.md

@@ -125,7 +125,7 @@ Reconsider `optimization.splitChunks`:
 
 - It's recommended to use either the defaults or `optimization.splitChunks: { chunks: 'all' }`.
 - When using a custom configuration, drop `name: false` and replace `name: string | function` with `idHint: string | function`.
-- It was possible to turn off the defaults by setting `optimization.splitChunks: { default: false, vendors: false }`. We don't recommend doing this, but if you really want to get the same effect in webpack 5: `optimization.splitChunks: { default: false, defaultVendors: false }`.
+- It was possible to turn off the defaults by setting `optimization.splitChunks.cacheGroups: { default: false, vendors: false }`. We don't recommend doing this, but if you really want to get the same effect in webpack 5: `optimization.splitChunks.cacheGroups: { default: false, defaultVendors: false }`.
 
 Consider removing defaults: