No need to limit to non-decimal rational answers in completing_the_square_2

fix #48573

Test plan: http://localhost:8000/exercises/completing_the_square_2.html?seed=171&problem=odds&debug&activity=%5B%5B%22incorrect-activity%22%2C%22%5B%5B%5C%222.5%5C%22%2C%5C%22.25%5C%22%2C%5C%22-3%5C%22%2C%5C%22-2%5C%22%5D%5D%22%2C152%5D%2C%5B%22hint-activity%22%2C%220%22%2C51%5D%2C%5B%22hint-activity%22%2C%220%22%2C9%5D%2C%5B%22hint-activity%22%2C%220%22%2C9%5D%2C%5B%22hint-activity%22%2C%220%22%2C19%5D%2C%5B%22hint-activity%22%2C%220%22%2C37%5D%2C%5B%22hint-activity%22%2C%220%22%2C8%5D%2C%5B%22incorrect-activity%22%2C%22%5B%5B%5C%222.5%5C%22%2C%5C%22.25%5C%22%2C%5C%22-3%5C%22%2C%5C%22-2%5C%22%5D%5D%22%2C9%5D%2C%5B%22incorrect-activity%22%2C%22%5B%5B%5C%222.5%5C%22%2C%5C%22.25%5C%22%2C%5C%22-2%5C%22%2C%5C%22-3%5C%22%5D%5D%22%2C7%5D%2C%5B%22incorrect-activity%22%2C%22%5B%5B%5C%222.5%5C%22%2C%5C%22.25%5C%22%2C%5C%22-2%5C%22%2C%5C%22-3%5C%22%5D%5D%22%2C23%5D%5D

Auditors: alpert