6 files declare their use of PluginCallerTrait in Backup and Migrate 8.4

BackupMigrate.php in lib/backup_migrate_core/src/Main/BackupMigrate.php

BrowserDownloadDestination.php in lib/backup_migrate_core/src/Destination/BrowserDownloadDestination.php

FileDirectorySource.php in lib/backup_migrate_core/src/Source/FileDirectorySource.php

MetadataWriter.php in lib/backup_migrate_core/src/Filter/MetadataWriter.php

MySQLiSource.php in lib/backup_migrate_core/src/Source/MySQLiSource.php

Notify.php in lib/backup_migrate_core/src/Filter/Notify.php