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

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