[WOM-5377][BpkComponentCalendar] Remove deferCallback for date formatters

[gwright170]

Removes deferIdleCallback strategy for improving Backpack Calendar Interaction to Next Paint (INP). For Skyscanner employees this can be read about in more detail at Optimising date formatter call stack.

We have found that requestIdleCallback introduces non-determinism in integration tests where data are not consistently added to the HTML in time. We have since resolved the primary performance issue in date formatting and this strategy should no longer be required.

Remember to include the following changes:

• Ensure the PR title includes the name of the component you are changing so it's clear in the release notes for consumers of the changes in the version e.g [KOA-123][BpkButton] Updating the colour
• README.md (If you have created a new component)
• Component README.md
• Tests
• Accessibility tests
  • The following checks were performed:
    • Ability to navigate using a keyboard only
    • Zoom functionality (Deque University explanation):
      • The page SHOULD be functional AND readable when only the text is magnified to 200% of its initial size
      • Pages must reflow as zoom increases up to 400% so that content continues to be presented in only one column i.e. Content MUST NOT require scrolling in two directions (both vertically and horizontally)
    • Ability to navigate using a screen reader only
• Storybook examples created/updated
• For breaking changes or deprecating components/properties, migration guides added to the description of the PR. If the guide has large changes, consider creating a new Markdown page inside the component's docs folder and link it here

[github-actions]

Visit https://backpack.github.io/storybook-prs/3702 to see this build running in a browser.

[github-actions]

	Warnings
⚠️	Package source files (e.g. packages/package-name/src/Component.js) were updated, but snapshots weren't. Have you checked that the tests still pass?
⚠️	Package source files (e.g. packages/package-name/src/Component.tsx) were updated, but type files weren't. Have you checked that no types have changed?

Browser support

If this is a visual change, make sure you've tested it in multiple browsers.

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