Bump dayjs from 1.8.17 to 1.8.21 (mui#1550)

Bumps [dayjs](https://github.com/iamkun/dayjs) from 1.8.17 to 1.8.21.
- [Release notes](https://github.com/iamkun/dayjs/releases)
- [Changelog](https://github.com/iamkun/dayjs/blob/dev/CHANGELOG.md)
- [Commits](iamkun/dayjs@v1.8.17...v1.8.21)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

docs/package.json

@@ -40,7 +40,7 @@
  "babel-plugin-module-resolver": "^3.2.0",
  "clsx": "^1.0.2",
  "date-fns": "^2.0.0",
- "dayjs": "^1.8.6",
+ "dayjs": "^1.8.21",
  "formik": "^1.5.1",
  "fuzzy-search": "^3.0.1",
  "isomorphic-fetch": "^2.2.1",

yarn.lock

@@ -4306,10 +4306,10 @@ date-now@^0.1.4:
  resolved "https://registry.yarnpkg.com/date-now/-/date-now-0.1.4.tgz#eaf439fd4d4848ad74e5cc7dbef200672b9e345b"
  integrity sha1-6vQ5/U1ISK105cx9vvIAZyueNFs=
 
-dayjs@^1.8.6:
- version "1.8.17"
- resolved "https://registry.yarnpkg.com/dayjs/-/dayjs-1.8.17.tgz#53ec413f2a7b02afbea1846d61bb260fa8567cea"
- integrity sha512-47VY/htqYqr9GHd7HW/h56PpQzRBSJcxIQFwqL3P20bMF/3az5c3PWdVY3LmPXFl6cQCYHL7c79b9ov+2bOBbw==
+dayjs@^1.8.21:
+ version "1.8.21"
+ resolved "https://registry.yarnpkg.com/dayjs/-/dayjs-1.8.21.tgz#98299185b72b9b679f31c7ed987b63923c961552"
+ integrity sha512-1kbWK0hziklUHkGgiKr7xm59KwAg/K3Tp7H/8X+f58DnNCwY3pKYjOCJpIlVs125FRBukGVZdKZojC073D0IeQ==
 
 debug@2.6.9, debug@^2.2.0, debug@^2.3.3:
  version "2.6.9"