Update jquery dependency

[marteki]

This update of jquery resolves a security warning we've received.

(I looked into removing jQuery entirely since we don't use it on our actual pages, but some of our tests rely on it. Maybe we should look into whether there's a good/better alternative for those tests?)

Changes

• Increment the requested jQuery version in package.json

Testing

• Pull the repo down, and run ./setup.sh. It should build without any failures.

Review

• @Scotchester
• @jimmynotjim

Checklist

• [x] Changes are limited to a single goal (no scope creep)
• [x] Code can be automatically merged (no conflicts)
• [x] Code follows the standards laid out in the front end playbook
• [x] Passes all existing automated tests
• [x] New functions include new tests
• [x] New functions are documented (with a description, list of inputs, and expected output)
• [x] Placeholder code is flagged
• [x] Visually tested in supported browsers and devices
• [x] Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)