fix parking=sheds description (#2130)

Author: k-yle

data/fields/parking.json

@@ -38,7 +38,7 @@
             },
             "sheds": {
                 "title": "Sheds",
-                "description": "Private hangars for vehicles."
+                "description": "Sheds for vehicle storage."
             },
             "layby": {
                 "title": "Turnout / Lay-By",