Changed classification of ice_cream and chocolate (#1628)

According to [OpenMapTiles Schema](https://openmaptiles.org/schema/) ice_cream should be a class, not a subclass of the shop, so I think it makes more sense to remove ice_cream from the shop class. I tested this, and after the change, both amenity=ice_cream and shop=ice_cream OSM tags get class=ice_cream + subclass=ice_cream, which is fine, because both OSM tags shop=ice_cream and amenity=ice_cream represents the same thing

The next thing I did was to change the color of the ice_cream icon.

layers/poi/style.json

@@ -22,7 +22,13 @@
             ]
           ]
         },
-        "icon-image": "{subclass}",
+        "icon-image": [
+          "match",
+          ["get", "subclass"],
+          "chocolate",
+          "confectionery",
+          ["get", "subclass"]
+        ],
         "text-field": "{name:latin}\n{name:nonlatin}",
         "visibility": "visible",
         "text-anchor": "top",
@@ -99,7 +105,13 @@
             ]
           ]
         },
-        "icon-image": "{subclass}",
+        "icon-image": [
+          "match",
+          ["get", "subclass"],
+          "chocolate",
+          "confectionery",
+          ["get", "subclass"]
+        ],
         "text-field": "{name:latin}\n{name:nonlatin}",
         "visibility": "visible",
         "text-anchor": "top",