hack: remove code generation related to generated files

With the removal of the protobuf for the controller, there are no longer
any generated files. Remove the makefile targets and the associated
dockerfiles and bake targets.

This wasn't being included in CI because it wasn't part of the
`validate` target.

Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>

docker-bake.hcl

@@ -98,13 +98,6 @@ target "validate-authors" {
   output = ["type=cacheonly"]
 }
 
-target "validate-generated-files" {
-  inherits = ["_common"]
-  dockerfile = "./hack/dockerfiles/generated-files.Dockerfile"
-  target = "validate"
-  output = ["type=cacheonly"]
-}
-
 target "update-vendor" {
   inherits = ["_common"]
   dockerfile = "./hack/dockerfiles/vendor.Dockerfile"
@@ -130,13 +123,6 @@ target "update-authors" {
   output = ["."]
 }
 
-target "update-generated-files" {
-  inherits = ["_common"]
-  dockerfile = "./hack/dockerfiles/generated-files.Dockerfile"
-  target = "update"
-  output = ["."]
-}
-
 target "mod-outdated" {
   inherits = ["_common"]
   dockerfile = "./hack/dockerfiles/vendor.Dockerfile"