Yesterday, our Wikibase Secondary CI on GitHub for changes merged to Wikibase master broke.
It seems the immidiate cause is [phpunit: Deprecate suite.xml and composer phpunit:entrypoint (If2ffe052)](https://gerrit.wikimedia.org/r/c/mediawiki/core/+/937980/) coming from [⚓ T227900 Phase out usage of tests/phpunit/suite.xml](https://phabricator.wikimedia.org/T227900).
The last successful Wikibase Secondary CI run had
```
[...]
+ cd ../mediawiki
+ composer phpunit:entrypoint -- --group Wikibase
> phpunit '-c' 'tests/phpunit/suite.xml' '--group' 'Wikibase'
Using PHP 7.4.33
[...]
```
but the failing ones now have
```
[...]
+ cd ../mediawiki
+ composer phpunit:entrypoint -- --group Wikibase
> phpunit '--group' 'Wikibase'
PHPUnit 9.5.28 by Sebastian Bergmann and contributors.
Usage:
phpunit [options] UnitTest.php
phpunit [options] <directory>
Code Coverage Options:
[...]
```
**Acceptance criteria**
* [ ] Wikibase Seconday CI is green again
* [ ] email sending works again, with a somehow more robust solution