bump receptor runtime-schema

[delivers #79618180]

Submodule src/github.com/cloudfoundry-incubator/receptor 78a3cd2..6fab1fd:
  > Add StopActualLRPsByProcessGuidAndIndex to Client
Submodule src/github.com/cloudfoundry-incubator/runtime-schema 5ab13bc..1544133:
  > Add RequestStopLRPInstances to ReceptorBBS

Signed-off-by: Eric Malm <emalm@pivotal.io>