Fix #839 incorrect clip_timestamps being used in model

[nonnoxer]

Changed the code from updating the TranscriptionOptions class instead of the options object (transcribe.py, lines 493-500), which likely was the cause of the unexpected behaviour of clip_timestamps not updating when calling transcribe multiple times

Original:

TranscriptionOptions.clip_timestamps=[
    float(ts)
    for ts in (
        options.clip_timestamps.split(",")
        if options.clip_timestamps
        else []
    )
]

Updated:

options = options._replace(
  clip_timestamps=[
      float(ts)
      for ts in (
          options.clip_timestamps.split(",")
          if options.clip_timestamps
          else []
      )
  ]
)