The Integration.get_configs() in Djblets allows for filtering of

configurations based on fields on the configuration model. Review Board

adopted this as well, but we don't actually want to expose this.

Instead, callers should be operating based on the contents of the

configuration's settings, which must be done manually anyway.
This cleans up the documentation for this method, and removes the custom

filtering.

Tested that the Slack integration still worked.