Remove former_administrative_division class

This needs more considiration

Author: David Karlaš

counterexamples/divisions/division/bad-geographical-region.yaml

@@ -17,4 +17,4 @@ properties:
         subtype: geographical_region
         name: A division with an invalid class.
   ext_expected_errors:
-    - value must be one of 'megacity', 'city', 'town', 'village', 'hamlet', 'disputed', 'region', 'former_administrative_division'
+    - value must be one of 'megacity', 'city', 'town', 'village', 'hamlet', 'disputed', 'region'

schema/divisions/division.yaml

@@ -66,9 +66,6 @@ properties:     # JSON Schema: Top-level object properties.
 
           - region        #A general geographical region.
                           #Example: Middle east.
-          - former_administrative_division # A division that no longer exists, but is still relevant as people
-                                           # often search for it.
-                                           # Example: Sogn og Fjordane, Norway.
       local_type:
         description:
           Local name for the subtype property, optionally localized.