Issue #3297233 by Project Update Bot: Automated Drupal 10 compatibility fixes

src/Component/Utility/FillPdf.php

src/OutputHandler.php

src/Plugin/FillPdfActionPlugin/FillPdfRedirectAction.php

src/Plugin/PdfBackend/PdftkPdfBackend.php

...les/fillpdf_test/src/Plugin/PdfBackend/TestPdfBackend.php

tests/src/Functional/FillPdfFormDeleteFormTest.php

tests/src/Functional/FillPdfFormDuplicateFormTest.php

tests/src/Functional/FillPdfFormImportFormTest.php

tests/src/Functional/FillPdfSettingsFormTest.php

tests/src/Functional/FillPdfTestBase.php

tests/src/Functional/LinkManipulatorTest.php

tests/src/Functional/PdfPopulationTest.php

tests/src/Functional/PdfWebformPopulationTest.php

tests/src/Functional/UninstallTest.php

tests/src/Kernel/FillPdfKernelTestBase.php

tests/src/Traits/TestFillPdfTrait.php