Add translation for merged actors in data history

backend/fr/data_history.json

@@ -27,6 +27,7 @@
         "provenance": "Provenance report",
         "image": "Image",
         "condition": "Condition",
-        "series": "Linked with object group"
+        "series": "Linked with object group",
+        "persinst_merge": "Actor entry merged"
     }
 }