Go vendor update

vendor/github.com/prometheus/client_golang/prometheus/metric.go

@@ -20,11 +20,9 @@ import (
 	"strings"
 	"time"
 
-	//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
-	"github.com/golang/protobuf/proto"
-	"github.com/prometheus/common/model"
-
 	dto "github.com/prometheus/client_model/go"
+	"github.com/prometheus/common/model"
+	"google.golang.org/protobuf/proto"
 )
 
 var separatorByteSlice = []byte{model.SeparatorByte} // For convenient use with xxhash.
@@ -94,6 +92,9 @@ type Opts struct {
 	// machine_role metric). See also
 	// https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels-not-static-scraped-labels
 	ConstLabels Labels
+
+	// now is for testing purposes, by default it's time.Now.
+	now func() time.Time
 }
 
 // BuildFQName joins the given three name components by "_". Empty name