bump garden
bump garden

[finishes #103986448]

Submodule src/github.com/cloudfoundry-incubator/garden 312b053..824a864:
  > Remove request content-type check

Signed-off-by: Alberto Leal <5dc1f959f7a95a292a4c05038be744ad597dff10@pivotal.io>
Signed-off-by: Petar Petrov <f705c0aa8aaf6bd313d55f7f3f71a8729abdecaa@gmail.com>

cloudfoundry-incubator/guardian-release,cloudfoundry-incubator/guardian-release,cloudfoundry-incubator/guardian-release