Remove master role from MySQL server
I'll get to the answer shortly, but first I should say I'm not sure why it is that you are trying to remove a "master role" from a host. Basically, a host is not configured "as master". Slaves just connect to it, which makes it a master.

I'm just curious: is this a security issue or something, that you want to forcibly prevent slaves from connecting to this host?

Anyway, one very easy way to do this is to remove the log-bin parameter, and restart MySQL. This will prevent MySQL from generating binary logs. No binary logs means slaves have nothing to get from this host, hence it cannot be a master.

Otherwise you may try and control that in terms of privileges. I don't think this is a good idea because this slave of yours will normally replicate everything from its master, including the privileges set on the master. So setting the slave to have a different (stricter?) set of privileges means it's not entirely in sync with its master.

Oh, and you may just grant the replication privilege on a pre-defined set of hosts, that would do the trick as well: 

GRANT REPLICATION SLAVE ON *.* TO 'replication'@'192.168.2.101' IDENTIFIED BY '123456';