[fix][test] Fix testPerTopicStats (#22870)

Signed-off-by: Zixuan Liu <[email protected]>

Author: nodece

Diff for: pulsar-broker/src/test/java/org/apache/pulsar/broker/stats/PrometheusMetricsTest.java

@@ -316,7 +316,7 @@ public void testPerTopicStats() throws Exception {
         assertEquals(cm.size(), 1);
         assertEquals(cm.get(0).tags.get("cluster"), "test");
 
-        cm = (List<Metric>) metrics.get("topic_load_failed_total");
+        cm = (List<Metric>) metrics.get("topic_load_failed");
         assertEquals(cm.size(), 1);
         assertEquals(cm.get(0).tags.get("cluster"), "test");