whisper : add single-timestamp logic (#2629)

whisper : add single-timestamp logic (#2629)

* Fix hallucinations during silence

When the predicted tokens end with a single timestamp the the entire 30 segment should be considered as done, to avoid hallucinations for the remaining part of segment.
This behaviour is on par with openai's whisper. Refer to logic related to `single_timestamp_ending` in https://github.com/openai/whisper/blob/main/whisper/transcribe.py

* Accept review comments related to formatting.

Co-authored-by: Georgi Gerganov <redacted>
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Co-authored-by: Georgi Gerganov <redacted>