dict: remove incorrect TODO in train_dictionary()
dict: remove incorrect TODO in train_dictionary()

I can find no ref counting leak unique to this code branch.
PyList_GetItem returns a borrowed ref.
terrelln/python-zstandard,indygreg/python-zstandard,indygreg/python-zstandard,terrelln/python-zstandard,terrelln/python-zstandard,indygreg/python-zstandard,terrelln/python-zstandard,indygreg/python-zstandard