bump atc
bump atc

Submodule src/github.com/concourse/atc 6ee7507..31a6297:
  > bindata

cjcjameson/concourse,concourse/concourse,concourse/concourse,cjcjameson/concourse,cjcjameson/concourse,concourse/concourse,concourse/concourse,concourse/concourse