fix: remove chrono dependency

[loloicci]

Description

chrono has a security issue (chronotope/chrono#499) and it is not fixed in the latest version.

We use chrono only in an example, so this PR removes chrono from the dependency.

Types of changes

• Bug fix (changes which fixes an issue)
• New feature (changes which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• ETC (build, ci, docs, perf, refactor, style, test)

Checklist

• I followed the contributing guidelines.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• The PR title and commits are followed conventional commit form.

[SeedyROM]

Could I get an explanation as to why this branch was closed? Been looking into the chrono vuln from chronotope/chrono#499 and haven't found much help or a minimal reproducible example yet. Maybe I haven't dug far enough.