[_removed] yarn --flat from CI configuration
It was being silently ignored because of pundle-dev's broken uws dependency. As soon as I fixed that and the caches cleared, CI started breaking because there are conflicts in devDependencies's transitive dependencies that haven't been addressed in resolutions.
Because yarn hoists by default, and the packages themselves don't have many dependencies, --flat is probably unnecessary. Having a bunch of resolutions for devDependencies is more likely to cause problems than allowing each dev dependency to have whatever version of a thing it wanted.
Tags: Material Motion
Differential Revision: http://codereview.cc/D3487