test/kubernetes: use zero-value TextParser until prometheus/common is bumped

expfmt.NewTextParser was introduced in a later prometheus/common
release than the one pinned here (v0.59.1), so every CoreDNS PR
that runs the Kubernetes test step fails with:

  ./metrics_test.go:87:15: undefined: expfmt.NewTextParser

Revert that call site to the zero-value `var tp expfmt.TextParser`
pattern (which defaults to legacy validation) so the job compiles
on the currently pinned dependency. Once go.mod's prometheus/
common is bumped to a version that exports NewTextParser (see
coredns/coredns#7731), this can be re-applied without the compat
note.

Also drop the now-unused prometheus/common/model import.

Signed-off-by: SAY-5 <SAY-5@users.noreply.github.com>

Author: SAY-5

test/kubernetes/metrics_test.go

@@ -10,7 +10,6 @@ import (
 
 	dto "github.com/prometheus/client_model/go"
 	"github.com/prometheus/common/expfmt"
-	"github.com/prometheus/common/model"
 	api "k8s.io/api/core/v1"
 	discovery "k8s.io/api/discovery/v1"
 	meta "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -85,7 +84,11 @@ func testEndpoints(t *testing.T, client *kubernetes.Clientset, slices bool) {
 
 	// scrape and parse metrics to get base state
 	m := ScrapeMetrics(t)
-	tp := expfmt.NewTextParser(model.LegacyValidation)
+	// prometheus/common v0.59.1 (pinned in go.mod) does not yet expose
+	// NewTextParser; stick with the zero-value TextParser, which
+	// defaults to legacy validation, until coredns/coredns#7731 bumps
+	// the common dep.
+	var tp expfmt.TextParser
 	base, err := tp.TextToMetricFamilies(strings.NewReader(string(m)))
 	if err != nil {
 		t.Fatalf("Could not parse scraped metrics: %v", err)