[Bug Report] Text-align issue for el-step icon

### Element UI version
2.14.1

### OS/Browsers version
macOS 10.15.6/Safari 14.1, Firefox 84.0b4

### Vue version
2.6.12

### Reproduction Link
https://jsfiddle.net/n34xq9h0/

### Steps to reproduce
1 The simple el-steps examples;
2 In parent element of el-steps, set style `text-align` to `center`/`right`.

### What is Expected?
Step icons (which were displayed as `inline-flex`) should be aligned to left;

### What is actually happening?
Step icon alignment was inherited from parent element of `el-steps`.