[Bug Report] When Table Expand uses components, if el-table-colum contains the property fixed="right", Created function is triggered twice

### Element UI version
2.15.0

### OS/Browsers version
Windows10 20H2 /Chomr 90.0.4430.212

### Vue version
2.6.12

### Reproduction Link
https://codepen.io/lujibao/pen/WNprQpV

### Steps to reproduce
el-table-colum contains the property fixed="right" of of father.vue,The created function in child.vue is executed twice.
If fixed="right" is not included, it is normal.

**The HTML of the link to reproduce the problem contains the Father. Vue page and the Child.Vue page**

### What is Expected?
The Child. vue created function is run once

### What is actually happening?
The Child. vue created function is run twice