Fix window end heuristic for hallucination_silence_threshold

[ryanheise]

Removes the end-of-window heuristic mentioned in #1838 (comment) which was causing it to (too) opportunistically skip over the silence at the end of the window when sometimes it was not in fact silence.

Its removal unmasks the similar block directly above it which should work well enough in this case:

                if not single_timestamp_ending:
                    last_word_end = get_end(current_segments)
                    if last_word_end is not None and last_word_end > time_offset:
                        seek = round(last_word_end * FRAMES_PER_SECOND)