fix minor code unreachability error

[Abirdcfly]

Signed-off-by: Abirdcfly fp544037857@gmail.com

https://pkg.go.dev/testing#T.Fatalf

Fatalf is equivalent to Logf followed by FailNow.

https://pkg.go.dev/testing#T.FailNow

FailNow marks the function as having failed and stops its execution by calling runtime.Goexit (which then runs all deferred calls in the current goroutine).

prometheus/discovery/marathon/marathon_test.go

Lines 161 to 166 in b57deb6

	if tg2.Source != tg1.Source {
	t.Fatalf("Source is different: %s != %s", tg1.Source, tg2.Source)
	if len(tg2.Targets) > 0 {
	t.Fatalf("Got a non-empty target set: %s", tg2.Targets)
	}
	}

So if line 162 use Fatalf, line163 to line 165 will never run.

[Abirdcfly]

TestUpdateMissedEvalMetrics Failed in test_windows @roidelapluie https://app.circleci.com/pipelines/github/prometheus/prometheus/17742/workflows/1397c0eb-0e24-42b9-b50c-43135bb63cbb/jobs/86103

I think rerun will fix it. But I do not have permission.

[roidelapluie]

Thanks