docs: update numeric type

src/nav-bar/README.md

@@ -59,7 +59,7 @@ export default {
 | left-arrow | Whether to show left arrow | *boolean* | `false` |
 | fixed | Whether to fixed top | *boolean* | `false` |
 | border | Whether to show bottom border | *boolean* | `true` |
-| z-index | Z-index | *string \| number* | `1` |
+| z-index | Z-index | *number \| string* | `1` |
 
 ### Slots
 

src/nav-bar/README.zh-CN.md

@@ -61,7 +61,7 @@ export default {
 | left-arrow | 是否显示左侧箭头 | *boolean* | `false` |
 | fixed | 是否固定在顶部 | *boolean* | `false` |
 | border | 是否显示下边框 | *boolean* | `true` |
-| z-index | 元素 z-index | *string \| number* | `1` |
+| z-index | 元素 z-index | *number \| string* | `1` |
 
 ### Slots