8 files declare their use of MarkupTrait in Drupal 10

BigPipeMarkup.php in core/modules/big_pipe/src/Render/BigPipeMarkup.php

FieldFilteredMarkup.php in core/lib/Drupal/Core/Field/FieldFilteredMarkup.php

FilteredMarkup.php in core/modules/filter/src/Render/FilteredMarkup.php

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

IFrameMarkup.php in core/modules/media/src/IFrameMarkup.php

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

TwigMarkupInterfaceTest.php in core/tests/Drupal/KernelTests/Core/Theme/TwigMarkupInterfaceTest.php

Contains \Drupal\KernelTests\Core\Theme\TwigMarkupInterfaceTest.

ViewsRenderPipelineMarkup.php in core/modules/views/src/Render/ViewsRenderPipelineMarkup.php