kamailio-install-guide-git: note that the lines with attributes may be commented

(cherry picked from commit e43e4cb63708b1147e6a701c459df512b08c091d)

kamailio-install-guide-git/docs/index.md

@@ -226,6 +226,9 @@ DBENGINE=MYSQL
 You can change other values in **kamctlrc** file, at least it is recommended to
 change the default passwords for the users to be created to connect to database.
 
+Note that the existing line with `DBENGINE` or other attributes may be commented,
+uncomment by removing the `#` character at the beginning of the line.
+
 Once you are done updating **kamctlrc** file, run the script to create the
 database used by Kamailio: