Allow migrate:import's --delete option to function

Dispatch the event name onMissingSourceRows is listening for.

drush-opsgh-5062

src/Drupal/Migrate/MigrateExecutable.php

@@ -259,7 +259,7 @@ protected function handleMissingSourceRows(MigrationInterface $migration): void
 
         if ($destinationIds) {
             $missingSourceEvent = new MigrateMissingSourceRowsEvent($migration, $destinationIds);
-            $this->getEventDispatcher()->dispatch($missingSourceEvent);
+            $this->getEventDispatcher()->dispatch($missingSourceEvent, MigrateMissingSourceRowsEvent::class);
         }
     }