chore(deps): bump chrono dependency

[orhun]

I'm using nvd_cve as a library and I was getting the following warning since the more recent version of chrono is pulled due to the loose versioning in Cargo.toml (0.4)

warning: use of deprecated associated function `chrono::NaiveDateTime::from_timestamp`: use `DateTime::from_timestamp` instead
   --> /home/orhun/gh/nvd_cve/src/feed.rs:116:36
    |
116 |                     NaiveDateTime::from_timestamp(0, 0)
    |                                    ^^^^^^^^^^^^^^
    |
    = note: `#[warn(deprecated)]` on by default

This PR updates chrono and fixes this warning.

[orhun]

I'm not sure why the CI fails 👀

[travispaul]

I'm not sure why the CI fails 👀

I'm not too concerned about the windows and MacOS builds. Those can be addressed later, as long as the Linux one is good.