corrected docstring and removed unused variable in featurize_binding_pocket_ecfp

  ----------

  protein_xyz: np.ndarray

    Of shape (N_protein_atoms, 3)

  protein: PDB object (TODO(rbharath): Correct?)

  protein: rdkit.rdchem.Mol

    Contains more metadata.

  ligand_xyz: np.ndarray

    Of shape (N_ligand_atoms, 3)

  ligand: PDB object (TODO(rbharath): Correct?)

  ligand: rdkit.rdchem.Mol

    Contains more metadata

  pairwise_distances: np.ndarray 

    Array of pairwise protein-ligand distances (Angstroms) 

  cutoff: float

    Cutoff distance for contact consideration.

  """

  features_dict = {}

  if pairwise_distances is None:

    pairwise_distances = compute_pairwise_distances(protein_xyz, ligand_xyz)