docs: fix duplicated word in document head management guide (#6565)

Author: pavan-sh

docs/router/framework/react/guide/document-head-management.md

@@ -89,7 +89,7 @@ export const Route = createRootRoute({
 
 ### Single-Page Applications
 
-First, remove the `<title>` tag from the the index.html if you have set any.
+First, remove the `<title>` tag from the index.html if you have set any.
 
 ```tsx
 import { HeadContent } from '@tanstack/react-router'