9 files declare their use of BlockCreationTrait in Drupal 10

AreaEntityTest.php in core/modules/views/tests/src/Kernel/Handler/AreaEntityTest.php

AreaOrderTest.php in core/modules/views/tests/src/Kernel/Handler/AreaOrderTest.php

BlockRebuildTest.php in core/modules/block/tests/src/Kernel/BlockRebuildTest.php

Breadcrumb404Test.php in core/tests/Drupal/FunctionalTests/Breadcrumb/Breadcrumb404Test.php

BrowserTestBase.php in core/tests/Drupal/Tests/BrowserTestBase.php

ConfigEntityImportTest.php in core/modules/system/tests/src/Kernel/Entity/ConfigEntityImportTest.php

NewDefaultThemeBlocksTest.php in core/modules/block/tests/src/Kernel/NewDefaultThemeBlocksTest.php

UnpublishedBlockTest.php in core/modules/block_content/tests/src/Functional/UnpublishedBlockTest.php

WorkspaceTestUtilities.php in core/modules/workspaces/tests/src/Functional/WorkspaceTestUtilities.php