OggWriter doesn't seem to need Seek

[Madoshakalaka]

trafficstars

I was trying to write an async adaptor and the Seek bound seems to make it impossible

https://github.com/webrtc-rs/webrtc/blob/1291594284f99706739e224913dc4bcd0c09a5e1/media/src/io/ogg_writer/mod.rs#L15

However, this bound seems totally unnecessary and unused. I removed all the Seek bounds and see no compile warnings.