docs: fix gtag plugin script source path in index.html

Author: devopvoid

docs/index.html

@@ -64,7 +64,7 @@
     <script src="//cdn.jsdelivr.net/npm/docsify-copy-code/dist/docsify-copy-code.min.js"></script>
     <script src="//cdn.jsdelivr.net/npm/prismjs@1/components/prism-java.min.js"></script>
     <script src="//cdn.jsdelivr.net/npm/prismjs@1/components/prism-gradle.min.js"></script>
-    <script src="//cdn.jsdelivr.net/npm/docsify@5/dist/plugins/gtag.min.js"></script>
+    <script src="//cdn.jsdelivr.net/npm/docsify/dist/plugins/gtag.min.js"></script>
     <script src="//unpkg.com/docsify-pagination/dist/docsify-pagination.min.js"></script>
 </body>
 </html>