Remove AWS dependency

[ivanjaros]

There is no place for such thing in a library like this. It can easily be made into additional library or custom code. But it should not be a dependency.

[piyongcai]

I think so too.

[rawnly]

it' used here for the tests i believe https://github.com/u2takey/ffmpeg-go/blob/master/examples/example_test.go

[IncredibleLaser]

I investigated this issue because of the file size of the resulting go binary which pointed to aws being the main culprit.

Anyhow, I don't use AWS and I'm not sure why it would be incorporated at ffmpeg wrapper level, but in case someone is curious, for my particular case, the binary built solely with go build shrank from 14MB to 4MB.