Tiny improvement for doc (#29581)
* Update add_new_model.md
* Update docs/source/en/add_new_model.md
Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>
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Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>
