Update which requirement from 7.0 to 8.0

[musicinmybrain]

This Pull Request fixes/closes #{issue_num}.v N/A

It changes the following:

• Updates the which dependency in Cargo.toml from 7.0 to 8.0
• Updates Cargo.lock with cargo update which.

I followed the checklist:

• I added unittests N/A, nothing new to test
• I ran make check without errors. (On Fedora 42, I needed to use CC=clang CXX=clang++ because onig_sys does not build with GCC 15 due to incompatible pointer types in the oniguruma C code. I also needed python-unversioned-command installed, and I needed to cargo install cargo sort. None of this has anything to do with this PR.)
• I tested the overall application
• I added an appropriate item to the changelog N/A, I think. It looks like you do not include dependency updates in the changelog.