docs(cascader): modify default value of placeholder (ant-design#49193)

components/cascader/index.en-US.md

@@ -70,7 +70,7 @@ Common props ref：[Common props](/docs/react/common-props)
 | notFoundContent | Specify content to show when no result matches | string | `Not Found` |  |
 | open | Set visible of cascader popup | boolean | - | 4.17.0 |
 | options | The data options of cascade | [Option](#option)\[] | - |  |
-| placeholder | The input placeholder | string | `Please select` |  |
+| placeholder | The input placeholder | string | - |  |
 | placement | Use preset popup align config from builtinPlacements | `bottomLeft` `bottomRight` `topLeft` `topRight` | `bottomLeft` | 4.17.0 |
 | showSearch | Whether show search input in single mode | boolean \| [Object](#showsearch) | false |  |
 | size | The input size | `large` \| `middle` \| `small` | - |  |

components/cascader/index.zh-CN.md

@@ -71,7 +71,7 @@ demo:
 | notFoundContent | 当下拉列表为空时显示的内容 | string | `Not Found` |  |
 | open | 控制浮层显隐 | boolean | - | 4.17.0 |
 | options | 可选项数据源 | [Option](#option)\[] | - |  |
-| placeholder | 输入框占位文本 | string | `请选择` |  |
+| placeholder | 输入框占位文本 | string | - |  |
 | placement | 浮层预设位置 | `bottomLeft` `bottomRight` `topLeft` `topRight` | `bottomLeft` | 4.17.0 |
 | showSearch | 在选择框中显示搜索框 | boolean \| [Object](#showsearch) | false |  |
 | size | 输入框大小 | `large` \| `middle` \| `small` | - |  |