修改`sheet`事件未调用的bug

src/main/java/com/alibaba/excel/util/WriteHandlerUtils.java

@@ -234,6 +234,6 @@ public class WriteHandlerUtils {
         } else {
             writeHandlerMap = writeContext.currentWriteHolder().writeHandlerMap();
         }
-        return writeHandlerMap.get(WorkbookWriteHandler.class);
+        return writeHandlerMap.get(clazz);
     }
 }