DatePicker: fix#22039 修复2.15.9 版本时间组件控制台报错

[chenchenwuai]

Please make sure these boxes are checked before submitting your PR, thank you!

• [x] Make sure you follow Element's contributing guide (中文 | English | Español | Français).
• [x] Make sure you are merging your commits to dev branch.
• [x] Add some descriptions and refer relative issues for you PR. 相关issue链接:

• https://github.com/ElemeFE/element/issues/22039
• https://github.com/ElemeFE/element/issues/22025
• https://github.com/ElemeFE/element/issues/21978
• https://github.com/ElemeFE/element/issues/21941

[MARIOMARUI]

居然没人管。

[MARIOMARUI]

为何我没有找到currentPlacement 的定义之处。

[chenchenwuai]

为何我没有找到currentPlacement 的定义之处。

在 src/utils/vue-popper 里面

[imba97]

居然没人管。

应该是有人已经修掉了 #21908