Downgraded @turf/union (see Turf.js issue #1392)

Author: sinergise-anze

package-lock.json

@@ -8,7 +8,7 @@
     "@turf/area": "^6.0.1",
     "@turf/helpers": "^6.1.4",
     "@turf/intersect": "^6.1.3",
-    "@turf/union": "^6.0.3",
+    "@turf/union": "^5.1.5",
     "@types/xml2js": "^0.4.4",
     "axios": "^0.18.1",
     "query-string": "^6.4.2",