[FLINK-32453] Ambiguous assertThat call after upgrade to Flink 1.18

This closes #39.
diff --git a/flink-connector-kafka/src/test/java/org/apache/flink/connector/kafka/source/enumerator/KafkaEnumeratorTest.java b/flink-connector-kafka/src/test/java/org/apache/flink/connector/kafka/source/enumerator/KafkaEnumeratorTest.java
index 3ced33f..b89f1b1 100644
--- a/flink-connector-kafka/src/test/java/org/apache/flink/connector/kafka/source/enumerator/KafkaEnumeratorTest.java
+++ b/flink-connector-kafka/src/test/java/org/apache/flink/connector/kafka/source/enumerator/KafkaEnumeratorTest.java
@@ -404,7 +404,7 @@
             assertThat(adminClient).isNotNull();
             String clientId = (String) Whitebox.getInternalState(adminClient, "clientId");
             assertThat(clientId).isNotNull().startsWith(clientIdPrefix);
-            assertThat(Whitebox.getInternalState(adminClient, "defaultApiTimeoutMs"))
+            assertThat((int) Whitebox.getInternalState(adminClient, "defaultApiTimeoutMs"))
                     .isEqualTo(defaultTimeoutMs);
 
             assertThat(clientId).isNotNull().startsWith(clientIdPrefix);