fix(operators.py): fix timediff typo
fix(operators.py): fix timediff typo

nzlosh/st2,StackStorm/st2,StackStorm/st2,StackStorm/st2,Plexxi/st2,nzlosh/st2,StackStorm/st2,Plexxi/st2,Plexxi/st2,nzlosh/st2,Plexxi/st2,nzlosh/st2