Summary:
Solves another acorn/minimist sec vuln. Also removed pins which
don't seem to be necessary anymore based on `yarn.lock` output
which seems to just remove them.
Pull Request resolved: https://github.com/facebook/flipper/pull/930
Test Plan: Ran `yarn build` and it still looks fine.
Reviewed By: mweststrate
Differential Revision: D20669831
Pulled By: passy
fbshipit-source-id: 8d82678cfac6304273aaf752b885edac91e0a8eb