Hi,
We can not modify the configuration when it is having the dependency. here Master redundancy is depended on VRRP hence you are not able to alter the VRRP configuration.
break the master redundancy from both the controllers.
for ref :
standby :
master-redundancy
(config-master-redundancy)#no master-vrrp
(config-master-redundancy)#no peer-ip-address
Repeat the same on the Master also. now you should be able to change the VIP.
Please feel free for any further help on this.