flake: update rust-overlay

This is just a bump to stay up-to-date.

On-behalf-of: SAP philipp.schuster@sap.com                                                                                  │1.1G   │ │   ┌─┴ pack                                                │██████░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░              │  10%
Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>

Author: phip1611