cmd/locktrigger: migrate to cloud.google.com message types

Done with:

go run cloud.google.com/go/internal/aliasfix/cmd/aliasfix@latest .
go mod tidy

As suggested in the package deprecation note¹.

¹ https://pkg.go.dev/google.golang.org/genproto/googleapis/devtools/cloudbuild/v1#pkg-overview

Change-Id: I5bc13274728839f3ef4df9aadda9634f46e1968c
Reviewed-on: https://go-review.googlesource.com/c/website/+/531701
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

cmd/locktrigger/main.go

@@ -47,8 +47,8 @@ import (
 	"time"
 
 	cloudbuild "cloud.google.com/go/cloudbuild/apiv1/v2"
+	"cloud.google.com/go/cloudbuild/apiv1/v2/cloudbuildpb"
 	"google.golang.org/api/iterator"
-	cloudbuildpb "google.golang.org/genproto/googleapis/devtools/cloudbuild/v1"
 )
 
 var (

go.mod

@@ -18,7 +18,6 @@ require (
 	golang.org/x/sync v0.3.0
 	golang.org/x/tools v0.13.0
 	google.golang.org/api v0.126.0
-	google.golang.org/genproto v0.0.0-20230530153820-e85fd2cbaebc
 	gopkg.in/yaml.v3 v3.0.1
 )
 
@@ -49,6 +48,7 @@ require (
 	golang.org/x/text v0.13.0 // indirect
 	golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2 // indirect
 	google.golang.org/appengine v1.6.7 // indirect
+	google.golang.org/genproto v0.0.0-20230530153820-e85fd2cbaebc // indirect
 	google.golang.org/genproto/googleapis/api v0.0.0-20230530153820-e85fd2cbaebc // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20230530153820-e85fd2cbaebc // indirect
 	google.golang.org/grpc v1.55.0 // indirect