Correct error message re length of service name

The error message had an off-by-one error :)

nomad/structs/structs.go

@@ -2267,7 +2267,7 @@ func (s *Service) ValidateName(name string) error {
 	// (https://tools.ietf.org/html/rfc2782).
 	re := regexp.MustCompile(`^(?i:[a-z0-9]|[a-z0-9][a-z0-9\-]{0,61}[a-z0-9])$`)
 	if !re.MatchString(name) {
-		return fmt.Errorf("service name must be valid per RFC 1123 and can contain only alphanumeric characters or dashes and must be less than 63 characters long: %q", name)
+		return fmt.Errorf("service name must be valid per RFC 1123 and can contain only alphanumeric characters or dashes and must be no longer than 63 characters: %q", name)
 	}
 	return nil
 }