Update lscolors from 0.20 to 0.21

[musicinmybrain]

The breaking change in 0.21.0 appears to be just that the crossterm dependency (re-exported when the crossterm feature is enabled) is updated to version 0.29.

This was once proposed by dependabot in #17226, but @fdncred wrote, “we'd have to update nu-ansi-term first.” Now, several months later, 007b223 has updated nu-ansi-term to the latest version, and this update doesn’t appear to have any messy consequences in Cargo.lock.

I confirmed that cargo test --workspace --exact --skip commands::network::http::helpful_dns_error_for_unknown_domain and cargo run -- -c "use toolkit.nu; toolkit test stdlib" still pass.

Release notes summary - What our users need to know

Tasks after submitting

• Update the documentation N/A

[fdncred]

Good catch. Thanks!