tests/fate/filter-video: Use a bitexact/lossless input sample for fate-filter-metadata-silencedetect
Signed-off-by: NMichael Niedermayer <michael@niedermayer.cc>

Set relevant filter parameters such that the result can easily be
checked with a waveform editor.
In particular, it makes it clear the silence_start is not accurate in
the current code.

The other information are just cluttering the output. The command line
is also simplified in the process.

Signed-off-by: NMichael Niedermayer <michaelni@gmx.at>