Fix typo in installation instructions

[mgmarlow]

Installation instructions for babel + NPM instructed installing the incorrect babel plugin.

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[goodmind]

@mgmarlow I thought there already was ton of PRs fixing this, but each next PR finds old babel plugin... Can you sign CLA?

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[mroch]

thanks!

@goodmind: there are at least 3 other PRs doing various conflicting things, in various needs of rebasing.

#6396 makes a similar change to a different part of the docs, which seems to have already been fixed
#6952 is similar to this PR, but it also updates babel-cli to @babel/cli and replaces some other references, which I think mostly have already been fixed by other PRs.
#7049 also switches to @babel/cli but additionally installs @babel/core. I have no idea if this is necessary.

since this one is current, it seems like the only one that can be merged without conflicts. I think we should probably update to @babel/cli and maybe add @babel/core. since we don't use this workflow internally, maybe you guys can help test that?

[mgmarlow]

@mroch sure I'll take a look. I set my project up using rollup so I didn't need the CLI but I can run through a similar flow with those tools.

[mgmarlow]

@mroch You're 100% correct, you also need @babel/core when running @babel/cli. I've updated the docs accordingly.

[mroch]

awesome, thank you! (and also @KidkArolis and @jeffvandyke for #7049)

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@mroch has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[facebook-github-bot]

@mroch merged this pull request in 955e926.