allergies: add test case for score of 257 (#1969)

Added test case
As mentioned in instructions the program shall only report the eggs (1) allergy for a given score of 257.

Author: karstenj

exercises/allergies/canonical-data.json

@@ -566,6 +566,17 @@
             "pollen",
             "cats"
           ]
+        },
+        {
+          "uuid": "93c2df3e-4f55-4fed-8116-7513092819cd",
+          "description": "no allergen score parts without highest valid score",
+          "property": "list",
+          "input": {
+            "score": 257
+          },
+          "expected": [
+            "eggs"
+          ]
         }
       ]
     }