docs: improve classname typing (#7927)

src/tab/README.md

@@ -267,7 +267,7 @@ export default {
 | to | Target route of the link, same as to of vue-router | _string \| object_ | - |
 | replace | If true, the navigation will not leave a history record | _boolean_ | `false` |
 | title-style | Custom title style | _any_ | - |
-| title-class | Custom title class name | _any_ | - |
+| title-class | Custom title class name | _string \| Array \| object_ | - |
 
 ### Tabs Events
 

src/tab/README.zh-CN.md

@@ -274,7 +274,7 @@ export default {
 | to | 点击后跳转的目标路由对象，同 vue-router 的 [to 属性](https://router.vuejs.org/zh/api/#to) | _string \| object_ | - |
 | replace | 是否在跳转时替换当前页面历史 | _boolean_ | `false` |
 | title-style | 自定义标题样式 | _any_ | - |
-| title-class | 自定义标题类名 | _any_ | - |
+| title-class | 自定义标题类名 | _string \| Array \| object_ | - |
 
 ### Tabs Events