bpo-41117: Cleanup subtract_refs() (GH-27593)

subtract_refs() reuses the 'op' variable rather than calling the
FROM_GC() macro twice.

Issue reported by William Pickard.

Victor Stinner committed 4y ago

c34fa2bb06ea44045af8493dfa414addb2b7ce66

Parent: cee67fa

Committed by GitHub <noreply@github.com> on 8/4/2021, 4:09:14 PM