Update python-dateutil requirement from <2.8 to <2.9

Updates the requirements on [python-dateutil](https://github.com/dateutil/dateutil) to permit the latest version.
- [Release notes](https://github.com/dateutil/dateutil/releases)
- [Changelog](https://github.com/dateutil/dateutil/blob/master/NEWS)
- [Commits](dateutil/dateutil@2.1...2.8.2)

---
updated-dependencies:
- dependency-name: python-dateutil
  dependency-type: direct:production
...

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

setup.py

@@ -50,7 +50,7 @@
     "chardet<4.0",
     "pymongo>=3.8,<3.12",
     "croniter<0.4",
-    "python-dateutil<2.8",
+    "python-dateutil<2.9",
     "unidecode==0.04.21",
     "authlib>0.14,<0.15",
     "draftjs-exporter[lxml]<2.2",