gitlab editing labels UpdateLabel function URL

Created by: threemay

PUT /projects/:id/labels/:label_id from the doc https://docs.gitlab.com/ee/api/labels.html#edit-an-existing-label

For the UpdateLabel function https://github.com/xanzy/go-gitlab/blob/098437be4ce2607448e2dfa5aaa8509e4e2ac475/labels.go#L224C2-L224C61 u := fmt.Sprintf("projects/%s/labels", PathEscape(project))