docs: note release which deprecated certain BBS API endpoints
docs: note release which deprecated certain BBS API endpoints

These were endpoints for which we added new revisions because of the image-layer work in https://www.pivotaltracker.com/story/show/158949366.

[#161385457](https://www.pivotaltracker.com/story/show/161385457)

cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release