Allow promql benchmarks to query more samples (prometheus#4770)

Signed-off-by: Chris Marchbanks <csmarchbanks@gmail.com>

promql/bench_test.go

@@ -32,7 +32,7 @@ func BenchmarkRangeQuery(b *testing.B) {
 		Logger:        nil,
 		Reg:           nil,
 		MaxConcurrent: 10,
-		MaxSamples:    10,
+		MaxSamples:    50000000,
 		Timeout:       100 * time.Second,
 	}
 	engine := NewEngine(opts)