Add requires.tables to <layer>.yaml (#1236)

**NOTE** this can only be merged after the next tools version is released.

Added required Postgres tables to the `<layer>.yaml` definition.
Close: #1220

PR of tools: https://github.com/openmaptiles/openmaptiles-tools/pull/370

layers/landuse/landuse.yaml

@@ -1,5 +1,8 @@
 layer:
   id: "landuse"
+  requires:
+    tables:
+      - ne_50m_urban_areas
   description: |
       Landuse is used to describe use of land by humans. At lower zoom levels this is
       from Natural Earth data for residential (urban) areas and at higher zoom levels mostly OSM `landuse` tags.