Add strict types - Update 5 files
- /tests/src/Kernel/ConnectionTester/ConnectionTesterTest.php
- /tests/src/Kernel/MigrateD7SettingsTest.php
- /tests/src/Kernel/ValidateD7MigrationStateTest.php
- /tests/src/Unit/Plugin/Mail/SMTPMailSystemTest.php
- /tests/src/Unit/SMTPConfigFormTest.php