fix: message/notification demos not auto-dismissing due to wrong duration unit (#8168)

duration was written as 2500 (intended as ms), but ant-design-vue's
message/notification duration is in seconds, so it was interpreted as
2500s (~41min), making the popups appear to never close.
Changed to 2.5 with a comment documenting the unit.

Closes #8144

apps/web-antd/src/views/demos/antd/index.vue

@@ -12,7 +12,8 @@ function info() {
 function error() {
   message.error({
     content: 'Once upon a time you dressed so fine',
-    duration: 2500,
+    // ant-design-vue 的 message.duration 单位是「秒」, 不是毫秒
+    duration: 2.5,
   });
 }
 
@@ -25,7 +26,8 @@ function success() {
 
 function notify(type: NotificationType) {
   notification[type]({
-    duration: 2500,
+    // ant-design-vue 的 notification.duration 单位是「秒」, 不是毫秒
+    duration: 2.5,
     message: '说点啥呢',
     type,
   });