Update split_silence.py

changes will resolve an error raised for some media files having bad and unprintable metadata ``` Traceback (most recent call last): File "/code/main.py", line 285, in <module> transform(item) File "/code/main.py", line 214, in transform chunk_dic = split_audio_and_chunk_to_dic(in_filename=f'./rx/some_file', File "/code/split_silence.py", line 313, in split_audio_and_chunk_to_dic chunk_times = get_chunk_times(in_filename, silence_threshold, silence_duration, start_time, end_time) File "/code/split_silence.py", line 149, in get_chunk_times output = p.communicate()[1].decode('utf-8') UnicodeDecodeError: 'utf-8' codec can't decode byte 0xa9 in position 1888: invalid start byte ```