* gc.c (gc_start_internal, rb_gc): do not need
  heap_pages_free_unused_pages() here.
  It was done in after_sweep().
* gc.c (rb_gc): The reason is now GPR_FLAG_CAPI.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44029 b2dd03c8-39d4-4d8f-98ff-823fe69b080e