Ruby

Remove debugging code from gc.c

Partially revert adab82b9a71f60ad1c7f4f8c134a5ae9198ab32a and
c63b5c6179d700ceacf5cae8d3ee86da1294c781.
The issue that these commits attempt to address was maybe fixed with
1c7f5a57125001447dc6173847dc68aa50bd8e93.