Issue #3217709 by sudiptadas19, mondrake: Replace usages of assertRegExp(), that is deprecated

...tests/src/Kernel/Migrate/d7/MigrateAggregatorFeedTest.php

core/modules/dblog/tests/src/Functional/DbLogTest.php

core/modules/jsonapi/tests/src/Functional/EntryPointTest.php

...es/jsonapi/tests/src/Functional/JsonApiFunctionalTest.php

core/modules/system/tests/src/Functional/Form/FormTest.php

.../tests/Drupal/FunctionalTests/Routing/PathEncodedTest.php

core/tests/Drupal/KernelTests/AssertContentTrait.php

core/tests/Drupal/KernelTests/Core/Command/DbDumpTest.php

...sts/Drupal/KernelTests/Core/Config/ConfigImporterTest.php

...upal/KernelTests/Core/Entity/EntityQueryAggregateTest.php

...ests/Drupal/KernelTests/Core/Menu/MenuTreeStorageTest.php

core/tests/Drupal/KernelTests/KernelTestBaseTest.php

core/tests/Drupal/Tests/Composer/ComposerTest.php

.../tests/Drupal/Tests/Core/Lock/LockBackendAbstractTest.php

...l/Tests/Core/StringTranslation/TranslatableMarkupTest.php

core/tests/Drupal/Tests/Core/Test/PhpUnitTestRunnerTest.php

...tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php

core/tests/Drupal/Tests/Scripts/TestSiteApplicationTest.php