fix(08): fix typo
fix(08): fix typo

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