Remove extensions of Array.prototype

[staxmanade]

We all know this is a bad practice, especially in a 3rd party utility/tool like Approvals.

Luckily it only happens at the end of a process so it's less likely to interfere with other's code, but still it's ugly...

There are several extensions that need to be refactored and remove the native prototype modification.

• Array.prototype.unique
• Array.prototype.selectMany