To "remove" (actually this only increase the fps limit but it will be enough to play using a 144 Hz monitor) you need to edit the server's KillingFloor.ini.

• Open KillingFloor.ini (server)
  
• Find [IpDrv.TcpNetDriver]
  
• Change MaxInternetClientRate to 15000
  
• Save

Remember to do this with the server closed.
Important: This is server side, changing this in your game will not allow you to get more than 90 FPS. If you don't have a server, you can try to host one yourself, buy one or find a server that allows more than 90 FPS.
You can also play solo or host a listen server.

You also need to edit the game User.ini

• Open KillingFloor.ini (game)
  
• Find [Engine.LevelInfo]
  
• Change MaxClientFrameRate to 150
  
• Save

• Open User.ini (game)
  
• Find [Engine.Player]
  
• Change ConfiguredInternetSpeed to 15000
  
• Save

I recommend disabling dynamic net speed. If you don't set ConfiguredInternetSpeed to 15000, you will need to type netspeed=15000 in the console every time you join a server/change map.