cleanup: remove commented out import in binary_code.py

Removed the unnecessary commented-out import of `_binary_polynomial`
in `src/openfermion/ops/operators/binary_code.py` to improve code
cleanliness and maintainability.

Author: mhucka

src/openfermion/ops/operators/binary_code.py

@@ -19,8 +19,6 @@
 
 from openfermion.ops.operators import BinaryPolynomial
 
-# import openfermion.ops.operators._binary_polynomial as bp
-
 
 def shift_decoder(decoder, shift_constant):
     """Shifts the indices of a decoder by a constant.