Tests have started failing for reasons that may be related to puppeteer's
Meteor process management: https://circleci.com/gh/meteor/meteor/31035
Since I can't identify any other possible causes, using the same version
of puppeteer that other tests use (e.g. modules, dynamic-import) seems
like a reasonable first step.
Also updated puppeteer in tests/apps/app-config/package-lock.json to
version 1.6.2 (was 1.3.0), in an attempt to fix some unhandled promise
rejection warnings: https://circleci.com/gh/meteor/meteor/31063
