Issue #1944646 by c960657: Remove CacheBackendInterface::deleteExpired().

core/lib/Drupal/Core/Cache/BackendChain.php

core/lib/Drupal/Core/Cache/CacheBackendInterface.php

core/lib/Drupal/Core/Cache/DatabaseBackend.php

core/lib/Drupal/Core/Cache/MemoryBackend.php

core/lib/Drupal/Core/Cache/NullBackend.php

...es/system/lib/Drupal/system/Tests/Cache/CacheTestBase.php

core/modules/system/system.module