Corrected Kernel#Array's signature

[sampersand]

This updates Kernel#Array to the correct signature.

The Array() function works as follows:

1. If the argument is an array, it's returned immediately
2. If the argument defines to_ary, then the return value of that is returned
3. If the argument defines to_a, then the return value of that is returned.
4. Otherwise, the argument is boxed up in an array and returned.

[ParadoxV5]

nil is already a _ToA (a nit, NilClass#to_a RBS also gives [ ] rather than []),
and Array is already a _ToAry and a _ToA

Suggested change

	def self?.Array: (nil) -> [ ]
	| [T] (Array[T] x) -> Array[T]
	| [T] (_ToAry[T] x) -> Array[T]
	def self?.Array: [T] (_ToAry[T] x) -> Array[T]

Though we can keep them for readability.

• Array(an_array)… programmers probably know what they are doïng.
• Array(nil) … will rubyists think this give [nil] instead?
  • Array(nilable)… I guess this one doesn’t matter that much since there’s Array(array_or_element_or_nil)

[sampersand]

Yeah, I was keeping it for readability. I don't think people will think Array nil #=> [nil] personally

[ParadoxV5]

If the lack of clarifications does not confuse people then it’s fine to omit them. WDYT, they who merges PRs?

[sampersand]

Consolidated in #1445