Remove gogoproto.stdtime

This commit removes gogoproto.stdtime, since it is not supported by
Google's official toolchain
(see https://github.com/containerd/containerd/issues/6564).

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

leases/proxy/manager.go

@@ -22,6 +22,7 @@ import (
 	leasesapi "github.com/containerd/containerd/api/services/leases/v1"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/leases"
+	"github.com/containerd/containerd/protobuf"
 )
 
 type proxyManager struct {
@@ -53,7 +54,7 @@ func (pm *proxyManager) Create(ctx context.Context, opts ...leases.Opt) (leases.
 
 	return leases.Lease{
 		ID:        resp.Lease.ID,
-		CreatedAt: resp.Lease.CreatedAt,
+		CreatedAt: protobuf.FromTimestamp(resp.Lease.CreatedAt),
 		Labels:    resp.Lease.Labels,
 	}, nil
 }
@@ -84,7 +85,7 @@ func (pm *proxyManager) List(ctx context.Context, filters ...string) ([]leases.L
 	for i := range resp.Leases {
 		l[i] = leases.Lease{
 			ID:        resp.Leases[i].ID,
-			CreatedAt: resp.Leases[i].CreatedAt,
+			CreatedAt: protobuf.FromTimestamp(resp.Leases[i].CreatedAt),
 			Labels:    resp.Leases[i].Labels,
 		}
 	}