internal/task: opt x/vuln in for updates only

x/vuln opted out of automatic tagging, but there's no reason for it not
to receive automatic updates. Also see a motivating data point captured
in https://go.dev/issue/56530#issuecomment-1342988547.

Now that there's a more fine-grained method of controlling whether to
tag a repo, move the decision there and stop ignoring the entire vuln
repo.

For golang/go#59686.
For golang/go#56530.

Change-Id: I32815b3d52d7bd2e601b4eae0290008b33eefbec
Reviewed-on: https://go-review.googlesource.com/c/build/+/525655
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

cmd/relui/main.go

@@ -277,7 +277,6 @@ func main() {
 	for p, r := range repos.ByGerritProject {
 		ignoreProjects[p] = !r.ShowOnDashboard()
 	}
-	ignoreProjects["vuln"] = true // x/vuln only has manual tagging for now. See issue 59686.
 	tagTasks := &task.TagXReposTasks{
 		IgnoreProjects: ignoreProjects,
 		Gerrit:         gerritClient,

internal/task/tagx.go

@@ -78,6 +78,10 @@ type TagRepo struct {
 // UpdateOnlyAndNotTag reports whether repo
 // r should be updated only, and not tagged.
 func (r TagRepo) UpdateOnlyAndNotTag() bool {
+	if r.Name == "vuln" {
+		return true // x/vuln only has manual tagging for now. See go.dev/issue/59686.
+	}
+
 	// Consider a repo without an existing tag as one
 	// that hasn't yet opted in for automatic tagging.
 	return r.StartVersion == ""