chore(Districts): Manually fix missing entries

Author: cblanc

data/districts.json

@@ -262,6 +262,8 @@
   "E08000035": "Leeds",
   "E08000036": "Wakefield",
   "E08000037": "Gateshead",
+  "E08000038": "Barnsley",
+  "E08000039": "Sheffield",
   "E09000001": "City of London",
   "E09000002": "Barking and Dagenham",
   "E09000003": "Barnet",
@@ -363,4 +365,4 @@
   "W06000022": "Newport",
   "W06000023": "Powys",
   "W06000024": "Merthyr Tydfil"
-}
+}