update after 2.0.0

CTFd updated to 2.0.0 which broke most plugins as they changed how all the utils load.

Ive managed to replace all the util calls except one which is referenced from the plugin: keys which is no longer used.

Wondering if you are able to help with patching this plugin to work with the latest version of CTFd (now 3.0.0)

the code that doesnt work now is:
` # Anti-bruteforce / submitting keys too quickly
if utils.get_kpm(session['id']) > 10:
`