remove duplicate key in build_slaves hash
remove duplicate key in build_slaves hash

buildbot/buildbot-infra,seankelly/buildbot-infra,seankelly/buildbot-infra,djmitche/buildbot-infra,djmitche/buildbot-infra,seankelly/buildbot-infra,djmitche/buildbot-infra,buildbot/buildbot-infra,buildbot/buildbot-infra