fix: update header title to reflect MinerU version 2.5

mineru/resources/header.html

@@ -54,7 +54,7 @@
             font-family: 'Trebuchet MS', 'Lucida Sans Unicode',
               'Lucida Grande', 'Lucida Sans', Arial, sans-serif;
           ">
-          MinerU 2: PDF Extraction Demo
+          MinerU 2.5: PDF Extraction Demo
         </h1>
       </div>
     </div>