Bump bigdecimal from 0.4.0 to 0.4.2

[cakebaker]

This PR bumps bigdecimal from 0.4.0 to 0.4.2 as a (partial?) solution for #6281. I didn't upgrade to 0.4.3 because it breaks a lot of seq tests and according to akubera/bigdecimal-rs#127 (comment) they will revert some of its changes in 0.4.4:

Version 0.4.3 changed the formatting in a way many people didn't like, so I'm changing formatting again for 0.4.4.

[BenWiederhake]

Looks good, tests are green except a single flake on CI:

---- test_install::test_install_and_strip stdout ----
run: /Users/runner/work/coreutils/coreutils/target/x86_64-apple-darwin/debug/coreutils install -s helloworld_macos helloworld_installed
thread 'test_install::test_install_and_strip' panicked at 'called `Result::unwrap()` on an `Err` value: Custom { kind: Other, error: "wait: Timeout of '30s' reached" }', tests/common/util.rs:1708:35