lean: 3.3.0 -> 3.4.1

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/lean/versions.

These checks were done:

- built on NixOS
- ran ‘/nix/store/kdbjdracd2m6fv18k9kc5bcmr0p60glx-lean-3.4.1/bin/lean -h’ got 0 exit code
- ran ‘/nix/store/kdbjdracd2m6fv18k9kc5bcmr0p60glx-lean-3.4.1/bin/lean --help’ got 0 exit code
- ran ‘/nix/store/kdbjdracd2m6fv18k9kc5bcmr0p60glx-lean-3.4.1/bin/leanpkg help’ got 0 exit code
- found 3.4.1 with grep in /nix/store/kdbjdracd2m6fv18k9kc5bcmr0p60glx-lean-3.4.1
- directory tree listing: https://gist.github.com/198504c00746718749b3019653fe78fd