While this is not strictly required, because removal will
happen in PHPUnit 9.0, we are already getting rid of all
uses in core.
From release notes:https://phpunit.de/announcements/phpunit-8.html
assertInternalType() is deprecated and will be removed in
PHPUnit 9. Refactor your test to use assertIsArray(), assertIsBool(),
assertIsFloat(), assertIsInt(), assertIsNumeric(), assertIsObject(),
assertIsResource(), assertIsString(), assertIsScalar(),
assertIsCallable(), or assertIsIterable() instead.
Eloy Lafuente (stronk7)