[Bug Report] Nesting a form within an el-table and simultaneously using 'fixed' and 'ref' can result in the issue of generating two 'ref' references.

### Element UI version
2.11.1

### OS/Browsers version
Chrome 版本 119.0.6045.199（正式版本） (arm64)

### Vue version
2.6.1

### Reproduction Link
https://github.com/moli1231/vue2_study

### Steps to reproduce
启动项目之后，访问该项目的地址，默认的路由页面中会有一个表格，表格中有三列，点击测试数据1这一列中的数据，会显示出来一个input表单，但是由于使用了fixed，会导致生成两个ref，此处将代码中的fixed属性去掉，则可以正常只有一个ref；但是生成了两个，就会导致通过ref操作这个input就有问题了

After launching the project, when accessing the project's address, the default route page will contain a table with three columns. Clicking on the data in the "Test Data 1" column will display an input form. However, due to the use of the fixed property, it results in the creation of two references. Removing the fixed property from the code resolves the issue, ensuring that only one reference is present. However, the presence of two references causes problems when manipulating this input through the reference.

### What is Expected?
只生成一个ref

### What is actually happening?
生成了两个ref（同一名称，两个值）