[Bug] Add a timeline and set the parameter "timeline. controllStyle. itemSize". The style and size of the "forward" and "backward" buttons will not take effect

### Version

5.5.1

### Link to Minimal Reproduction

https://echarts.apache.org/examples/zh/editor.html?c=doc-example%2Fmix-timeline-all&edit=1&reset=1&version=5.5.1

### Steps to Reproduce

Add code blocks to the code block timeline：
` controlStyle: {
position: 'left',
itemSize:10
},`

### Current Behavior

The style and size of the "forward" and "backward" buttons do not take effect

### Expected Behavior

Expect the styles and sizes of the "forward" and "backward" buttons to take effect

### Environment

```markdown
- OS: macOS
- Browser:Chrome 128.0.6613.137
- Framework:Vue@3
```

### Any additional comments?

_No response_