[FLINK-36945] Tweak to make the container static so it could be reused across multiple test cases

Author: yoheimuta

flink-cdc-connect/flink-cdc-source-connectors/flink-connector-mysql-cdc/src/test/java/org/apache/flink/cdc/connectors/mysql/source/MySqlMultipleTablesRenamingITCase.java

@@ -80,7 +80,7 @@ public class MySqlMultipleTablesRenamingITCase {
     @RegisterExtension static MiniClusterExtension miniCluster = new MiniClusterExtension();
 
     @SuppressWarnings("unchecked")
-    private final MySqlContainer mysql =
+    private static final MySqlContainer mysql =
             (MySqlContainer)
                     new MySqlContainer()
                             .withConfigurationOverride(