Remove unused osm_boundary_linestring and boundary mapping

layers/boundary/boundary.yaml

@@ -27,6 +27,3 @@ layer:
     query: (SELECT geometry, admin_level, disputed, maritime FROM layer_boundary(!bbox!, z(!scale_denominator!))) AS t
 schema:
   - ./boundary.sql
-datasources:
-  - type: imposm3
-    mapping_file: ./mapping.yaml

layers/boundary/mapping.yaml

@@ -1,20 +0,0 @@
-tables:
-  # etldoc: imposm3 -> osm_boundary_linestring
-  boundary_linestring:
-    fields:
-    - name: osm_id
-      type: id
-    - name: geometry
-      type: geometry
-    - key: admin_level
-      name: admin_level
-      type: integer
-    filters:
-      reject:
-        natural:  ["coastline"]
-      require:
-        admin_level: ["__any__"]
-    mapping:
-      boundary:
-      - administrative
-    type: linestring