multimedia/ffmpeg: Remove celt support

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Summary

It's been deprecated by upstream (Xiph) and obsolete since 2016, it's also not enabled by default in FFmpeg

PR: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=258656

Test Plan

Poudriere testport OK 12.2-RELEASE (amd64)

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Bump portrevision

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Committed as 2870caaf323abba4a61ed1851c2e73cb18758b24