Remove checking of reference counts after collection

Because of reference loops, there is no guarantee that
reference count of an object after collection will be
the same as before.

E.g. deleting module M containing class C.
After M is deleted (from main module), M is still
referenced as module(C), C is still referenced inside
dict(M).  A string S is still referenced as name(M).
Thus, before collection, ref_cnt(S) == 1, but after
collection, ref_cnt(S) == 0, and therefore,
ref_cnt(#String) will be one less after collection
than before.