Update mysqlclient requirement from <2.2.1 to <2.2.4

Updates the requirements on [mysqlclient](https://github.com/PyMySQL/mysqlclient) to permit the latest version.
- [Release notes](https://github.com/PyMySQL/mysqlclient/releases)
- [Changelog](https://github.com/PyMySQL/mysqlclient/blob/main/HISTORY.rst)
- [Commits](PyMySQL/mysqlclient@MySQLdb-0.9.0b1...v2.2.3)

---
updated-dependencies:
- dependency-name: mysqlclient
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

test-requirements.txt

@@ -1,4 +1,4 @@
 factory-boy>=2.4
 testfixtures==7.2.2
 psycopg[binary]>=3.1
-mysqlclient<2.2.1
+mysqlclient<2.2.4