Arrow keys do not work in co-author select menu

[smashwilson]

Prerequisites

• Put an X between the brackets on this line if you have done all of the following:
  • Reproduced the problem in Safe Mode: https://flight-manual.atom.io/hacking-atom/sections/debugging/#using-safe-mode
  • Followed all applicable steps in the debugging guide: https://flight-manual.atom.io/hacking-atom/sections/debugging/
  • Checked the FAQs on the message board for common solutions: https://discuss.atom.io/c/faq
  • Checked that your issue isn't already filed: https://github.com/issues?utf8=✓&q=is%3Aissue+user%3Aatom
  • Checked that there is not already an Atom package that provides the described functionality: https://atom.io/packages

Description

The Select component used to choose co-authors within the CommitView does not allow you to navigate up and down the list with up and down arrows when the menu is open.

Note that this will also be an issue in #2222 - I discovered this problem in the "create repo" dialog there, but noticed that the existing co-author select has the same issue 😱

Steps to Reproduce

1. Open Atom on a project folder with a git repository that has a GitHub remote with a list of mentionable users (like atom/github). Open the git tab.
2. Expand the co-author form. Click in the text field to reveal the select menu. The (alphabetically) first mentionable user should be focused.
3. Press the "down" key.

Expected behavior:

The second mentionable user should be focused.

Actual behavior:

Nothing.

Reproduces how often:

100%

Versions

macOS 10.14.6

$ atom --version
Atom    : 1.42.0-nightly8
Electron: 4.2.7
Chrome  : 69.0.3497.128
Node    : 10.11.0
$ apm ls
# ...
Git Packages (1) /Users/smashwilson/.atom/packages
└── github@0.31.0 (atom/github#2e8726d5)

Additional Information

react-select has two major releases newer than the version we're using (the first of which was a total rewrite). My preference would be to upgrade react-select to the most recent version, then fix keyboard navigation to work again.