fix(tests): `gen` will be a keyword in Rust 2024

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #612 will degrade performances by 11.84%

_{Comparing push-qpltxumyknur (e86b884) with main (8adbf68)}

Summary

❌ 2 regressions ✅ 34 untouched benchmarks

:warning: Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	push-qpltxumyknur	Change
❌	Compare kuhn_munkres with different input sizes[256]	16.9 ms	19 ms	-10.68%
❌	Compare kuhn_munkres with different input sizes[512]	507 ms	575.1 ms	-11.84%