fix(02_Dependent_Type_Theory): fix Do_twice
fix(02_Dependent_Type_Theory): fix Do_twice

But hyphenation is not so nice now.

cjmazey/fork_leanprover_tutorial,leanprover/tutorial,avigad/tutorial,Hodapp87/cs6460_project,Hodapp87/cs6460_project,cjmazey/fork_leanprover_tutorial,fpvandoorn/tutorial,Hodapp87/cs6460_project,soonhokong/lean-tutorial,cjmazey/fork_leanprover_tutorial,soonhokong/lean-tutorial,soonhokong/lean-tutorial,fpvandoorn/tutorial,leanprover/tutorial,leanprover/tutorial,avigad/tutorial,fpvandoorn/tutorial,avigad/tutorial