Remove no longer needed park class functions

layers/park/class.sql

@@ -1,7 +0,0 @@
-CREATE OR REPLACE FUNCTION park_class(landuse TEXT, leisure TEXT, boundary TEXT) RETURNS TEXT AS $$
-    SELECT CASE
-        WHEN leisure = 'nature_reserve' OR boundary='national_park' THEN 'national_park'
-        WHEN landuse IN ('recreation_ground', 'village_green') or leisure = 'park' THEN 'public_park'
-         ELSE NULL
-     END;
-$$ LANGUAGE SQL IMMUTABLE;