disable unused extension todo
disable unused extension todo

We're not using todo extension of sphinx anywhere so there's no reason
for it to be included in conf.py

mpc-hc/mpc-hc.org,FeodorFitsner/mpc-hc.org,FeodorFitsner/mpc-hc.org,FeodorFitsner/mpc-hc.org,Underground78/mpc-hc.org,mpc-hc/mpc-hc.org,kasper93/mpc-hc.org,kasper93/mpc-hc.org,mpc-hc/mpc-hc.org,Underground78/mpc-hc.org,Underground78/mpc-hc.org