bump receptor
bump receptor

Submodule src/github.com/cloudfoundry-incubator/receptor b05df76..8a4cf02:
  > docs: add note about Content-Type header

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