Bump chrono dependency to fix panic

[rgwood]

Description

Bumping chrono to hopefully fix an issue reported on Discord:

hi, since 0.66.3, i get this when trying to run nu on aarch64 (rpi 4) https://paste.debian.net/1250272/
thanks
ls /root/.cargo/registry/src/github.com-1ecc6299db9ec823/chrono-0.4.20/src/offset/local/unix.rs
/root/.cargo/registry/src/github.com-1ecc6299db9ec823/chrono-0.4.20/src/offset/local/unix.rs

I'm unable to reproduce that on my Raspberry Pi, but it is probably this chrono issue which is fixed in v0.4.21

Update: user said they're on Void Linux, I'm on Debian 11. That's probably the real issue, not aarch64

Tests

Make sure you've done the following:

• Add tests that cover your changes, either in the command examples, the crate/tests folder, or in the /tests folder.
• Try to think about corner cases and various ways how your changes could break. Cover them with tests.
• If adding tests is not possible, please document in the PR body a minimal example with steps on how to reproduce so one can verify your change works.

Make sure you've run and fixed any issues with these commands:

• cargo fmt --all -- --check to check standard code formatting (cargo fmt --all applies these changes)
• cargo clippy --workspace --features=extra -- -D warnings -D clippy::unwrap_used -A clippy::needless_collect to check that you're using the standard code style
• cargo test --workspace --features=extra to check that all the tests pass

^I am currently unable to run that test on my machine because it OOMs, will let CI do it.