Matches https://github.com/ilyagr/pijul-clone as of now, might become out of sync

Bump flake.nix & flake.lock

Upgrading to Rust 1.70 allows usage of newly stabilised APIs such as std::sync::OnceLock and std::thread::available_parallelism.

Created by  finchie  on July 13, 2023
2RUJ4J7MBRP3N3FRDPS4CSSAXK6T6UWZAMS7RRDQSRNATERMPY4QC
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