Fix ArrayInput makes the form dirty in strict mode

[djhi]

Problem

Fixes #9661

Solution

We had a workaround for adding validation on the ArrayInput itself (like min/max number of items) that triggered a register/unregister of the input in react-hook-form inside a useEffect. This effect is run twice in StrictMode.
It appears the workaround isn't needed anymore to have validation on the ArrayInput.

How To Test

• https://react-admin-storybook-61vioyrs6-marmelab.vercel.app/?path=%2Fstory%2Fra-ui-materialui-input-arrayinput--basic To check the isDirty. Run the story locally for React.StrictMode
• https://react-admin-storybook-61vioyrs6-marmelab.vercel.app/?path=%2Fstory%2Fra-ui-materialui-input-arrayinput--validation To check validation is still working

Additional Checks

• The PR targets master for a bugfix, or next for a feature
• The PR includes unit tests (if not possible, describe why)
• The PR includes one or several stories (if not possible, describe why)
• The documentation is up to date

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