Fix missing tag for memorial=blue_plaque preset (#1689)

Author: hb0nd

data/presets/historic/memorial/blue_plaque-GB-IE.json

@@ -18,7 +18,8 @@
         "memorial": "blue_plaque"
     },
     "addTags": {
-        "historic": "memorial"
+        "historic": "memorial",
+        "memorial": "blue_plaque"
     },
     "name": "Blue Plaque",
     "locationSet": {