fix: pin @babel/parser to 7.16.8

[ehmicky]

Some builds are experiencing a big slowdown when we upgrade @babel/parser from 7.16.8 to 7.16.10 (note: there is no 7.16.9 release).

The only PR introduced by that release is babel/babel#14130, so it appears to have some issues. It could be one of the following bugs, but we are not sure yet: babel/babel#14182, babel/babel#14175

We are certain that the problem comes from this specific package and this specific version. We also know the problem comes from @babel/parser as a direct dependency of @netlify/zip-it-and-ship-it, as opposed to as an indirect dependency through precinct and node-source-walker.

This PR pins the version of @babel/parser until we figure out why this version is creating a problem on our side.

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[eduardoboucas]

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