fix: warn when passing `className` to `<PrismicRichText>` or `<PrismicText>`

Types of changes

[ ] Chore (a non-breaking change which is related to package maintenance)
[x] Bug fix (a non-breaking change which fixes an issue)
[ ] New feature (a non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)

This PR adds a development-only warning when a className prop is passed to the following components:

These components do not support a className prop, but their purpose suggests they do.

See the classname-is-not-a-valid-prop.md message for more details.

[ ] My change requires an update to the official documentation.
[x] All TSDoc comments are up-to-date and new ones have been added where necessary.
[x] All new and existing tests are passing.

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