Use DecisionLine in PyConf.tonic docs
Follows Moore!716 (merged). (Seeing as this MR doesn't change any code, it could be merged before Moore!716 (merged), assuming we're happy with the DecisionLine name such that it won't change.)
Follows Moore!716 (merged). (Seeing as this MR doesn't change any code, it could be merged before Moore!716 (merged), assuming we're happy with the DecisionLine name such that it won't change.)