Fixed citation.
Related issue: [Docs] update the last year in citation, 2020-2023 to 2020-2024 #1598
Milestone: https://github.com/lisphilar/covid19-sir/milestone/54?closed=1
What's Changed
- update the last year in citation, 2020-2023 to 2020-2024 by @lisphilar in #1599
Full Changelog: 3.1.0...3.1.1