MINOR: Fix typo in CoordinatorBackgroundThreadPoolExecutorTest (#21932)

Reviewers: Chia-Ping Tsai <chia7712@gmail.com>

Author: squah-confluent

coordinator-common/src/test/java/org/apache/kafka/coordinator/common/runtime/CoordinatorBackgroundThreadPoolExecutorTest.java

@@ -39,7 +39,7 @@ public void testMetrics() throws ExecutionException, InterruptedException, Timeo
         CoordinatorRuntimeMetrics metrics = mock(CoordinatorRuntimeMetrics.class);
         Time mockTime = new MockTime();
         CoordinatorBackgroundThreadPoolExecutor threadPoolExecutor = new CoordinatorBackgroundThreadPoolExecutor(
-            "threaad-pool-",
+            "thread-pool-",
             2,
             mockTime,
             metrics