[Bug Report] dialog和tooltip层级问题

### Element UI version
2.15.14

### OS/Browsers version
window，chrome131.0.6778.71

### Vue version
2.6.10

### Reproduction Link
https://element.eleme.cn/#/zh-CN/component/dialog

### Steps to reproduce
提示框打开次数小于弹框打开次数就会出现提示框的z-index大于弹框的z-index，出现提示框被弹框遮挡的问题

### What is Expected?
提示框总是在弹框上面，不会被遮挡

### What is actually happening?
bug，提示框会被弹框遮挡