Array#pop, Array#shift, Array#clear don't check whether array is frozen

[clayton-shopify]

> a = [1, 2, 3].freeze
 => [1, 2, 3]
> a.pop
 => 3
> a
 => [1, 2]
> a.shift
 => 1
> a
 => [2]
> a.clear
 => []

This issue was reported by https://hackerone.com/an0n-j