Update index.mdx

As per coderabbitai recommendation, fixed spelling of GitHub to proper capitalization.

Author: rowebil

docs/index.mdx

@@ -43,5 +43,5 @@ Pelican is open-source, allowing users to browse the code, contribute improvemen
 
 <Admonition type="warning" title="🔒 Reporting Security Issues 🔒">
     If you notice anything that raises a concern, please reach out directly to **team@pelican.dev**  
-    For security reasons, we ask that you handle security disclosures responsibly and **avoid posting them on Github.**
+    For security reasons, we ask that you handle security disclosures responsibly and **avoid posting them on GitHub.**
 </Admonition>