ports/stm: drop stale audioio sample_rate pot entry

Removed leftover msgid "sample_rate must be > 0" from
locale/circuitpython.pot. The raise was replaced with
mp_arg_validate_int_min in d42941d1a3 but the pot entry
was not regenerated.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>