update vendor

vendor/github.com/prometheus/common/model/time.go

@@ -186,6 +186,10 @@ var durationRE = regexp.MustCompile("^([0-9]+)(y|w|d|h|m|s|ms)$")
 // ParseDuration parses a string into a time.Duration, assuming that a year
 // always has 365d, a week always has 7d, and a day always has 24h.
 func ParseDuration(durationStr string) (Duration, error) {
+	// Allow 0 without a unit.
+	if durationStr == "0" {
+		return 0, nil
+	}
 	matches := durationRE.FindStringSubmatch(durationStr)
 	if len(matches) != 3 {
 		return 0, fmt.Errorf("not a valid duration string: %q", durationStr)