build(deps): update mysqlclient requirement from ~=2.2.5 to ~=2.2.6

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@v2.2.5...v2.2.6)

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

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

requirements-test.txt

@@ -1,4 +1,4 @@
-mysqlclient~=2.2.5
+mysqlclient~=2.2.6
 psycopg2-binary~=2.9.9
 sqlparse~=0.5.1
 python-dateutil~=2.9.0