Remove unused dateFormat prop

[ghsteff]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[x] Other... Please describe:

Does this PR introduce a breaking change?

[x] Yes (technically I guess?)
[ ] No

Other information

This props not getting used anywhere, and there's no date's being displayed in the calendar to use it on

date in this story's being displayed outside Calendar

[netlify]

✅ Deploy Preview for reablocks-storybook ready!

Name	Link
🔨 Latest commit	ba5e5f5
🔍 Latest deploy log	https://app.netlify.com/sites/reablocks-storybook/deploys/663cf59a8f2d1d00087acee4
😎 Deploy Preview	https://deploy-preview-172--reablocks-storybook.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.