[DRE-maint] open-build-service is marked for autoremoval from testing

[Debian testing autoremoval watch]

open-build-service 2.7.4-2 is marked for autoremoval from testing on 2018-04-22

It is affected by these RC bugs:
894778: open-build-service: open-build-service requires ruby2.3 for building

It (build-)depends on packages with these RC bugs:
861361: ruby-riddle: update build-depend to unversioned php-cli
893610: ruby-sanitize: CVE-2018-3740