Typo in bucc_extract() causing errors

[KeremZaman]

In utils_retrieve.py, the bucc_extract() function tries to use args.encoding from evaluate_retrieval.py arguments but args aren't passed to this function. Although the function bucc_eval(), which calls the bucc_extract(), has a parameter for encoding, it's not passed to bucc_extract() . Also args.encoding isn't passed to bucc_eval().

As a quick fix, adding optional parameter for encoding to bucc_extract() will solve the issue without changing many things.