10 files declare their use of Page in Page Manager 8.4

FrontPageTest.php in tests/src/Functional/FrontPageTest.php

PageConfigSchemaTest.php in tests/src/Kernel/PageConfigSchemaTest.php

PageManagerAdminTest.php in page_manager_ui/tests/src/Functional/PageManagerAdminTest.php

PageManagerAdminTest.php in page_manager_ui/tests/src/FunctionalJavascript/PageManagerAdminTest.php

PageManagerRoutingTest.php in tests/src/Kernel/PageManagerRoutingTest.php

PageNodeAccessTest.php in tests/src/Functional/PageNodeAccessTest.php

PagePlaceholderTest.php in tests/src/Functional/PagePlaceholderTest.php

PageTest.php in tests/src/Unit/PageTest.php

PageVariantPageEntityTest.php in tests/src/Kernel/PageVariantPageEntityTest.php

SerializationTest.php in tests/src/Kernel/SerializationTest.php