Markdown hover: links should use hover color

Similar to #121536, #121521, #125956

```js
"workbench.colorCustomizations": {
	"textLink.foreground": "#ffae00",
	"textLink.activeForeground": "#00a2ff",
}
```

1. Create markdown hover for Tree View
```ts
// @ts-ignore
get tooltip() {
	return new MarkdownString('[google](https://www.google.com)');
}
```
2. Hover over the link
3. Link is not using `textLink.activeForeground`