fixed small typo

README.md

@@ -11,7 +11,7 @@ More details about Kamailio at:
 ### Tutorials ###
 
   * __[kamailio-install-guide-git](https://github.com/kamailio/kamailio-docs/tree/master/kamailio-install-guide-git)__ - Install Kamailio From Git Repository
-  * __[kamailio-install-guide-deb](https://github.com/kamailio/kamailio-docs/tree/master/kamailio-install-guide-deb)__ - Install Kamailio On Debian (Rr Ubuntu) Using Packages
+  * __[kamailio-install-guide-deb](https://github.com/kamailio/kamailio-docs/tree/master/kamailio-install-guide-deb)__ - Install Kamailio On Debian (Or Ubuntu) Using Packages
 
 
 ### Support ###