bump fly
bump fly

[finishes #143697477]

Submodule src/github.com/concourse/fly 0634ce6..5c0d8e5:
  > Update fly integration tests to use image_resource #143697477
  > Update fly tests to use image_resource #143697477

concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse