Issue #3466788 by mondrake, longwave: Fix ‘risky’ tests

...ckeditor5/tests/src/Kernel/CKEditor5PluginManagerTest.php

...modules/ckeditor5/tests/src/Unit/HTMLRestrictionsTest.php

...igrate_drupal/tests/src/Unit/source/DrupalSqlBaseTest.php

core/modules/mysql/tests/src/Kernel/mysql/SchemaTest.php

core/modules/pgsql/tests/src/Kernel/pgsql/SchemaTest.php

core/phpunit.xml.dist

...re/DependencyInjection/Compiler/StackedKernelPassTest.php