Improve "second" and "day(s)" translation to Greek

[pothitos]

Pull Request Checklist

• 🧪 Added tests for changed code.
• 🛠️ All tests pass when run locally (run tox or make test to find out!).
• 🧹 All linting checks pass when run locally (run tox -e lint or make lint to find out!).
• 📚 Updated documentation for changed code.
• ⏩ Code is up-to-date with the master branch.

Description of Changes

Hello Jad and thanks for merging my previous pull request!

I finally migrated to this nice library and found another two improvements/fixes for the Greek translation (in accordance to humanize).

By the way, when do you plan to create a new PyPI package?

[jadchaar]

LGTM! Thanks for the contribution.