fix ExcelUtilsTest return

Author: hkun0120

dolphinscheduler-alert/dolphinscheduler-alert-plugins/dolphinscheduler-alert-email/src/test/java/org/apache/dolphinscheduler/plugin/alert/email/ExcelUtilsTest.java

@@ -66,7 +66,7 @@ public void testGenExcelFile() {
         Assertions.assertTrue(xlsFile.exists());
 
         // Invoke genExcelFile with incorrectContent, will cause RuntimeException
-        Assertions.assertThrows(AlertEmailException.class, () -> {
+        Assertions.assertThrows(IllegalArgumentException.class, () -> {
             ExcelUtils.genExcelFile(incorrectContent1, title, xlsFilePath);
         });