feat: [Translate] A new field mime_type is added to message .google.cloud.translation.v3.AdaptiveMtTranslateRequest (#9080)

* feat: A new field `mime_type` is added to message `.google.cloud.translation.v3.AdaptiveMtTranslateRequest`

PiperOrigin-RevId: 895422613

Source-Link: googleapis/googleapis@d6837a5

Source-Link: googleapis/googleapis-gen@cd509ea
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* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

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Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: gcf-owl-bot[bot]