Fix ruby2_keywords on Ruby 3.2

[casperisfine]

The first versions of ruby that introduced ruby2_keywords had a small bug, only the first method in a chain of call needed to mark itself as using ruby2_keywords smeantic, e.g.

def foo(a:); end

def bar(*args)
  foo(*args)
end

def baz(*args)
  bar(*args)
end
ruby2_keywords :baz

baz(a: 1)

Up to 3.1 the above cause no issue, however in 3.2, bar also need to be marked with ruby2_keywords.

[casperisfine]

👋 @t6d any chance to get this merged?