Remove `q:` style queries as an option for pipelines endpoints.

[rundquist]

The pipelines endpoints don't actually support this type of query.

[abarnwell]

The pipelines endpoints don't actually support this type of query.

It's so frustrating that they don't. It would be a very useful feature to query for all the pipelines that have run against a certain branch for example...I've had an open ticket with them for about a year now to extend querying to pipelines. :-(