Remove ‘Regions of England’ library

It made for a good early demo to show how we could have different
libraries, but we’d don’t think there’s a strong user need for being
able to broadcast to a region of England.

Regions also have the problem that:
- they are ambiguous – both England and Scotland have a region called
  ‘South east’
- Northern Ireland doesn’t have formal regions

This commit removes the regions library.

app/broadcast_areas/create-broadcast-areas-db.py

@@ -71,7 +71,6 @@ repo.create_tables()
 
 simple_datasets = [
     ("Countries", "ctry19cd", "ctry19nm"),
-    ("Regions of England", "rgn18cd", "rgn18nm"),
     ("Counties and Unitary Authorities in England and Wales", "ctyua16cd", "ctyua16nm"),
 ]
 for dataset_name, id_field, name_field in simple_datasets: