Update `bidmanager.createBid` docs with 2nd param
Update `bidmanager.createBid` docs with 2nd param

Addresses https://github.com/prebid/prebid.github.io/issues/168

prebid/prebid.github.io,prebid/prebid.github.io,sonobi/prebid.github.io,prebid/prebid.github.io,sonobi/prebid.github.io,sonobi/prebid.github.io