Add processInstance.setProcessDefinitionCode in UT (#6435)

dolphinscheduler-dao/src/test/java/org/apache/dolphinscheduler/dao/mapper/TaskInstanceMapperTest.java

@@ -66,6 +66,7 @@ public class TaskInstanceMapperTest {
         ProcessInstance processInstance = new ProcessInstance();
         processInstance.setWarningGroupId(0);
         processInstance.setCommandParam("");
+        processInstance.setProcessDefinitionCode(1L);
         processInstanceMapper.insert(processInstance);
         processInstanceId = processInstance.getId();
     }