fix(modals): update devDependency @zendeskgarden/css-modals to correct padding for various header/body/footer layouts

[jzempel]

• BREAKING CHANGE?

Description

Provide consistent header/body/footer stacking...

• whether or not a footer is included
• despite modal dialog element ordering
• for both default & large dialog sizes

Detail

See zendeskgarden/css-components#134 for details.

Checklist

• 👌 design updates are Garden Designer approved (add the
  designer as a reviewer)
• 💅 view component styling is based on a Garden CSS
  component
• 🌐 Styleguidist demo is up-to-date (yarn start)
• ⬅️ renders as expected with reversed (RTL) direction
• 💂‍♂️ includes new unit and snapshot tests
• 📒 any new files are included in the packages src/index.js export
• 📝 tested in Chrome, Firefox, Safari, Edge, and IE11

[coveralls]

Coverage remained the same at 94.781% when pulling 75c76fc on jzempel/modal-fix into 2a7c986 on master.

[austingreendev]

LGTM.

I'm going to hold off deployment until all of the Github data consistency issues are fixed. Otherwise the webhooks might not trigger Travis.