fix(fvt): reduce minimum compression-ratio metric

Batched test compression-ratio can sometimes be as low as 3

Signed-off-by: Dominic Evans <dominic.evans@uk.ibm.com>

functional_producer_test.go

@@ -1021,7 +1021,7 @@ func validateProducerMetrics(t *testing.T, client Client) {
 		// We record compression ratios of 1.00 (100 with a histogram) for every TestBatchSize record
 		if client.Config().Version.IsAtLeast(V0_11_0_0) {
 			// records will be grouped in batchSet rather than msgSet
-			metricValidators.registerForGlobalAndTopic("test_1", minCountHistogramValidator("compression-ratio", 4))
+			metricValidators.registerForGlobalAndTopic("test_1", minCountHistogramValidator("compression-ratio", 3))
 		} else {
 			metricValidators.registerForGlobalAndTopic("test_1", countHistogramValidator("compression-ratio", TestBatchSize))
 		}