Remove gogo from .proto files

While gogo isn't actually used, it is still referenced from .proto files
and its corresponding Go package is imported from the auto-generated
files.

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

pkg/runtimeoptions/v1/api.proto

@@ -3,8 +3,6 @@ syntax = "proto3";
 
 package runtimeoptions.v1;
 
-import "github.com/gogo/protobuf/gogoproto/gogo.proto";
-
 option go_package = "github.com/containerd/containerd/pkg/runtimeoptions/v1;runtimeoptions_v1";
 
 message Options {