Add test for Hash#each consistently yields a 2-element array

[JuanCrg90]

From #823

https://bugs.ruby-lang.org/issues/12706?tab=history

As a semantics, Hash#each yields a 2-element array (pairs of keys and
values). So, { a: 1 }.each(&->(k, v) { }) should raise an exception
due to lambda's arity check.

[JuanCrg90]

What do you think @eregon ?

[eregon]

Could you assert the message too? I think it'd help clarity.
Also it'd be good to test that it works fine with a lambda taking a single argument.

[eregon]

BTW it seems the same change applies to Hash#each_pair too, so could you move it to the core/hash/shared/each.rb shared spec?

[eregon]

Looks like it's already covered actually:

spec/core/hash/shared/each.rb

Lines 41 to 55 in 7376aa0

	ruby_version_is "3.0" do
	it "always yields an Array of 2 elements, even when given a callable of arity 2" do
	obj = Object.new
	def obj.foo(key, value)
	end
	-> {
	{ "a" => 1 }.send(@method, &obj.method(:foo))
	}.should raise_error(ArgumentError)
	-> {
	{ "a" => 1 }.send(@method, &-> key, value { })
	}.should raise_error(ArgumentError)
	end
	end

[eregon]

Sorry for the late review. In the shared spec it seems already tested, so I'll close this.