[Bug Report] this.$parent.computePresentText is not a function in el-cascader-panel component

### Element UI version
2.13.2

### OS/Browsers version
MacOS Mojave 10.14.6 / Chrome Version 83.0.4103.116 (Official Build) (64-bit)

### Vue version
2.6.11

### Reproduction Link
https://codepen.io/bulatie/pen/yLejzOZ

### Steps to reproduce
As codepen demo.

Similar issue: https://github.com/ElemeFE/element/issues/18664

### What is Expected?
Each value of level should be checked in its menu

### What is actually happening?
Just first value of level be selected, and third level menu is not able to show up.