message: Update Git stats description
diff: ## GitHub Contributors
  -As reported by [`git-stats -a -s '19 September 2014'`](https://www.npmjs.com/package/git-stats) analysis
  -of `master` as of Thu, 16 Sep 2021 after deduplication with `.mailmap`.
  +As reported by [`git-stats -a -s '2014'`](https://www.npmjs.com/package/git-stats) analysis
  +of `master` as of Tue, 5 Oct 2021 after deduplication with `.mailmap`.
  ![Top git contributors](screenshots/git-stats.png)
  