Message spam to opped players

[Solved]

I keep getting spammed messages for MythicMobs. How can I stop them from showing up?
http://prntscr.com/gglrhf

I use: MythicMobs-4.3.0-SNAPSHOT.jar
(If I remember correctly, higher versions didn't work)

Server: 1.10.2


Note: Sorry if I take a while to respond, I'm pretty busy with college.