fix: update link format for Ganeti RPM package upgrade documentation

Author: jfut

doc/update-rhel-3.0-to-3.1.md

@@ -6,7 +6,7 @@ Ganeti RPM Packaging for RHEL/CentOS/others.
 
 If you are updating from a version earlier than 2.16, see the document for 3.0.
 
-- [Update Ganeti RPM package from 2.16 to 3.0](https://github.com/jfut/ganeti-rpm/blob/master/doc/update-rhel-2.16-to-3.0.rst)
+- [Update Ganeti RPM package from 2.16 to 3.0](https://github.com/jfut/ganeti-rpm/blob/master/doc/update-rhel-2.16-to-3.0.md)
 
 Official documentation: