[Bug] graph vertical edge lines has wrong position

### Version

5.4.3 ~ 6.0.0

### Link to Minimal Reproduction

https://codepen.io/igincui/pen/LYMMeOE

### Steps to Reproduce

1. How do you create the chart.
Open the codepen link: https://codepen.io/igincui/pen/LYMMeOE

2. What's the chart option

```
option = {
series: [
{
type: 'graph',
roam: true,
symbolSize: [23, 28],
itemStyle: { opacity: 0.5, color: 'green' },
lineStyle: { opacity: 1.0, color: 'red' },
data: [
{
id: 'start',
x: -10,
y: 570,
symbol: 'path://M 0 0 h23 v28 h-23 v-28 z'
},
{
id: 'a',
x: -10,
y: 560,
symbol: 'path://M 0 0 h23 v28 h-23 v-28 z'
},
{
id: 'b',
x: 0,
y: 560,
symbol: 'path://M 0 0 h23 v28 h-23 v-28 z'
},
],
links: [
{
source: 'start',
target: 'a'
},
{
source: 'start',
target: 'b'
},
]
}
]
};
```

3. User interactions before the error happens.
None

### Current Behavior

The vertical lines have wrong positions, do not start from and end to the center of symbols.


### Expected Behavior

The vertical lines should have correct positions, start from and end to the center of symbols.

### Environment

```markdown
- OS: Win 10 (64-bit)
- Browser: Chrome Version 117.0.5938.149 ~ 141.0.7390.55 (Official Build) (64-bit)
- Framework: None
```

### Any additional comments?

None