Fix issue with `child_process.spawn` on Windows

[nathanhleung]

I don't think the .cmd hack is necessary anymore.

Upstream issue: nodejs/node#3675
Relevant issues/PRs in this repo: #123, #124

[TobiTenno]

@nathanhleung would we be able to remove it, then?

[nathanhleung]

@TobiTenno this issue seems related to #252, for which I just published a fix. Try it out and let me know if you're still encountering an issue.

[TobiTenno]

it's working for me on the 2 projects i've tried when they were on the right version of install-peerdeps. thanks for the fix!