fix(12): use '-- BEGIN' and '-- END'
fix(12): use '-- BEGIN' and '-- END'

instead of '--BEGIN' and '--END'

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