docs: fix type of devServer.hot (#7711)

docs: fix type of devServer.hot

Author: shulaoda

website/docs/en/config/dev-server.mdx

@@ -498,7 +498,7 @@ Specifying local-ipv6 as host will try to resolve the host option as your local
 
 ## devServer.hot
 
-- **Type:** `boolean`
+- **Type:** `boolean | 'only'`
 - **Default:** `true`
 
 Enable Rspack's Hot Module Replacement feature:

website/docs/zh/config/dev-server.mdx

@@ -487,7 +487,7 @@ module.exports = {
 
 ## devServer.hot
 
-- **类型：** `boolean`
+- **类型：** `boolean | 'only'`
 - **默认值：** `true`
 
 开启热更新：