services/horizon: cannot stream offers

[overcat]

According to the documentation, the offers endpoint can be used in streaming mode.

What version are you using?

2.15.1-e29c7803d487c3f5b44a74773e6277fee16482cf

What did you do?

Trying to stream offers, laboratory test request.

What did you expect to see?

A stream of offers.

What did you see instead?

{
  "type": "https://stellar.org/horizon-errors/not_acceptable",
  "title": "An acceptable response content-type could not be provided for this request",
  "status": 406
}

[overcat]

I think It is an error in the documentation, according to the code it is unstreamable.