Fix/rdkit qed module clean

[jiaodu1307]

Use QED module for QED score calculation
ref: https://www.rdkit.org/docs/source/rdkit.Chem.QED.html#rdkit.Chem.QED.qed

[Gonzih]

LGTM — correct fix with the right approach.

Descriptors.qed is a thin alias that internally delegates to rdkit.Chem.QED.qed, but the canonical RDKit API is QED.qed(mol). Using the module directly is clearer, more explicit, and consistent with how the rest of the codebase already imports and uses QED (the import line is updated correctly in the same diff to add QED to the existing import). Two-line change, no side effects.

[Gonzih]

Correct fix. Descriptors.qed does not exist — QED lives in its own rdkit.Chem.QED module. Adding the explicit import and calling QED.qed(mol) is the right approach per the RDKit docs. Clean and minimal.

Note: this file is also modified by PR #97. Whichever merges second will need a rebase. Both fixes touch different lines so the combination is straightforward.