fix(docs): Remove rspress-plugin-preview

rspress.config.ts

@@ -1,5 +1,4 @@
 import { defineConfig } from '@rspress/core';
-import { pluginPreview } from '@rspress/plugin-preview';
 import { pluginSitemap } from '@rspress/plugin-sitemap';
 import { pluginClientRedirects } from '@rspress/plugin-client-redirects';
 
@@ -41,7 +40,7 @@ export default defineConfig({
         },
     },
 
-    plugins: [pluginPreview(), pluginSitemap({
+    plugins: [pluginSitemap({
         siteUrl: 'https://continuwuity.org', // TODO: Set automatically in build pipeline
     }),
     pluginClientRedirects({