8 files declare their use of Variable in Drupal 9

Datetime.php in core/lib/Drupal/Core/Datetime/Element/Datetime.php

DatetimeElementFormTest.php in core/tests/Drupal/KernelTests/Core/Datetime/DatetimeElementFormTest.php

DbDumpCommand.php in core/lib/Drupal/Core/Command/DbDumpCommand.php

Extract.php in core/modules/migrate/src/Plugin/migrate/process/Extract.php

Renderer.php in core/lib/Drupal/Core/Render/Renderer.php

StaticMap.php in core/modules/migrate/src/Plugin/migrate/process/StaticMap.php

StaticMapTest.php in core/modules/migrate/tests/src/Unit/process/StaticMapTest.php

VariableTest.php in core/tests/Drupal/Tests/Component/Utility/VariableTest.php

Contains \Drupal\Tests\Component\Utility\VariableTest.