Remove enemies from the list of people, even if the enemy shows up twice.
remove_enemies(["Fred"], []) ➞ ["Fred"]
remove_enemies(["Adam", "Emmy", "Tanya", "Emmy"], ["Emmy"]) ➞ ["Adam", "Tanya"]
remove_enemies(["John", "Emily", "Steve", "Sam"], ["Sam", "John"]) ➞ ["Emily", "Steve"]
All names to be removed will be in the enemies list; simply return the list, no fancy strings.