py-pdm: updated to 2.9.3

Release v2.9.3 (2023-09-25)
---------------------------

Bug Fixes

- Revert the changes to the behavior of installing self.
Self package won't be installed when `--no-default` is requested.
- Reject the candidate if it contains invalid metadata, to avoid a crash in the process of resolution.

Documentation

- Clarify what `--no-isolated` does.

(adam)