fix: correctly format date conversion to a string for native date input

[yihuiliao]

Closes https://github.com/adobe/react-spectrum/issues/9064

should be fine to get rid of the timezone since this only updates the value passed to the hidden date input and won't be submitted to a form. since neither input type="date" or input type="datetime-local" support timezones, it makes sense to remove it.

✅ Pull Request Checklist:

• [ ] Included link to corresponding React Spectrum GitHub Issue.
• [ ] Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• [ ] Filled out test instructions.
• [ ] Updated documentation (if it already exists for this component).
• [ ] Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

Go to the RAC DateField Autofill and DatePicker Autofill story. Check the browser to make sure there aren't any console warnings. If autofill is supported (so far have only gotten it to work in Safari), clear the date in the field and try autofilling with your contact info.

🧢 Your Project: