chore: bump cronstrue from 2.14.0 to 2.21.0 in /site (#5545)

Bumps [cronstrue](https://github.com/bradymholt/cronstrue) from 2.14.0 to 2.21.0.
- [Release notes](https://github.com/bradymholt/cronstrue/releases)
- [Changelog](https://github.com/bradymholt/cRonstrue/blob/master/CHANGELOG.md)
- [Commits](https://github.com/bradymholt/cronstrue/compare/v2.14.0...v2.21.0)

---
updated-dependencies:
- dependency-name: cronstrue
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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site/package.json

@@ -46,7 +46,7 @@
     "chartjs-adapter-date-fns": "2.0.0",
     "color-convert": "2.0.1",
     "cron-parser": "4.7.0",
-    "cronstrue": "2.14.0",
+    "cronstrue": "2.21.0",
     "date-fns": "2.29.3",
     "dayjs": "1.11.4",
     "emoji-mart": "5.3.3",