[Bug Report] Stroke-linecap attribute of Progress is invalid, and so is element-plus

### Element UI version
2.15.9

### OS/Browsers version
chrome 103.0.5060.53

### Vue version
2.7.8

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

### Steps to reproduce
1.use stroke-linecap attribute of Progress

### What is Expected?
when the value of stroke-linecap is square, the ends of line should be square

### What is actually happening?
when the value of stroke-linecap is square, the ends of line is still round