docs: update component css vars value

src/pull-refresh/README.md

@@ -140,9 +140,9 @@ Use slots to custom tips.
 
 The component provides the following CSS variables, which can be used to customize styles. Please refer to [ConfigProvider component](#/en-US/config-provider).
 
-| Name                                 | Default Value   | Description |
-| ------------------------------------ | --------------- | ----------- |
-| --van-pull-refresh-head-height       | `50px`          | -           |
-| --van-pull-refresh-head-font-size    | `@font-size-md` | -           |
-| --van-pull-refresh-head-text-color   | `@gray-6`       | -           |
-| --van-pull-refresh-loading-icon-size | `16px`          | -           |
+| Name | Default Value | Description |
+| --- | --- | --- |
+| --van-pull-refresh-head-height | `50px` | - |
+| --van-pull-refresh-head-font-size | `var(--van-font-size-md)` | - |
+| --van-pull-refresh-head-text-color | `var(--van-gary-6)` | - |
+| --van-pull-refresh-loading-icon-size | `16px` | - |

src/pull-refresh/README.zh-CN.md

@@ -143,12 +143,12 @@ export default {
 
 组件提供了下列 CSS 变量，可用于自定义样式，使用方法请参考 [ConfigProvider 组件](#/zh-CN/config-provider)。
 
-| 名称                                 | 默认值          | 描述 |
-| ------------------------------------ | --------------- | ---- |
-| --van-pull-refresh-head-height       | `50px`          | -    |
-| --van-pull-refresh-head-font-size    | `@font-size-md` | -    |
-| --van-pull-refresh-head-text-color   | `@gray-6`       | -    |
-| --van-pull-refresh-loading-icon-size | `16px`          | -    |
+| 名称                                 | 默认值                    | 描述 |
+| ------------------------------------ | ------------------------- | ---- |
+| --van-pull-refresh-head-height       | `50px`                    | -    |
+| --van-pull-refresh-head-font-size    | `var(--van-font-size-md)` | -    |
+| --van-pull-refresh-head-text-color   | `var(--van-gary-6)`       | -    |
+| --van-pull-refresh-loading-icon-size | `16px`                    | -    |
 
 ## 常见问题