Fix formatting errors and commented code

Per review comments by @dstrain115.

Author: mhucka

src/openfermion/ops/operators/binary_code.py

@@ -295,7 +295,6 @@ def __rmul__(self, factor):
 
     def __str__(self):
         """Return an easy-to-read string representation."""
-        # string_return = [list(map(list, self.encoder.toarray()))]
 
         def convert_to_native(value):
             return getattr(value, "tolist", lambda: value)()