[SPARK-3970] Remove duplicate removal of local dirs

The shutdown hook of `DiskBlockManager` would remove localDirs. So do not need to register them with `Utils.registerShutdownDeleteDir`. It causes duplicate removal of these local dirs and corresponding exceptions.
Ah right. I really think deleteRecursively just shouldn't fail in this situation. If the dir can't be listed it should move on. Unfortunately `null` means "not a dir, or, an error occurred". So it may be resolvable by checking if the dir exists to begin with.