Revert "decode: copy the output parameters from the last bsf in the chain back to the AVCodecContext"

This reverts commit 662558f9.

The avcodec_parameters_to_context() call was freeing and reallocating
AVCodecContext->extradata, essentially taking ownership of it, which according
to the doxy is user owned. This is an API break and has produces crashes in
some library users like Firefox.
Revert until a better solution is found to internally propagate the filtered
extradata back into the decoder context.
Signed-off-by: James Almer <jamrial@gmail.com>