Quickfix for installing @type removes installed modules

[octref]

Testing #42358

1. Have a workspace that already installs request and lodash
2. Have a file like so

import * as _ from 'lodash'
import * as req from 'request'

3. Quick fix anyone of them by installing @types dependency
4. Notice many installed modules in your node_modules are gone

Before:

After:

[octref]

This happens when you have a node_modules installed using yarn (if using npm it seems work fine).

[mjbvz]

Thanks! Opened microsoft/TypeScript#21504 to track this upstream