fix: Use Cargo Clippy to avoid the `gen` reserved keyword

[heeckhau]

RUSTFLAGS="-D keyword_idents_2024" cargo clippy --fix fixes #180

[sinui0]

This is a fix, but I would rather rename instead of r#. rand will be changing gen to random in the next release. We may want to rename to Garbler

[sinui0]

Closing, I would prefer we avoid the r# solution