Fixed description to reference new layer name

layers/transportation/transportation.yaml

@@ -8,7 +8,7 @@ layer:
       It contains all roads from motorways to primary, secondary and
       tertiary roads to residential roads and
       foot paths. Styling the roads is the most essential part of the map.
-      The `highway` layer also contains polygons for things like plazas.
+      The `transportation` layer also contains polygons for things like plazas.
   buffer_size: 4
   srs: +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over
   fields: