Fix typo in highway areas definition

This solves a typo introduced by me in ccf558f.

This solves unexpected rendering of highway areas.

This solves gravitystorm#730.

project.mml

@@ -699,7 +699,7 @@
       ],
       "Datasource": {
         "type": "postgis",
-        "table": "(select way,coalesce(('highway_' || (case when highway in ('residential','unclassified','pedestrian','service','footway','cycleway','track','path','platform') then 'cycleway' else null end)), ('railway_' || (case when railway in ('platform') then railway else null end))) as feature from planet_osm_polygon\n       where highway in ('residential','unclassified','pedestrian','service','footway','track','path','platform')\n          or railway in ('platform')\n       order by z_order,way_area desc) as highway_area_casing",
+        "table": "(select way,coalesce(('highway_' || (case when highway in ('residential','unclassified','pedestrian','service','footway','cycleway','track','path','platform') then highway else null end)), ('railway_' || (case when railway in ('platform') then railway else null end))) as feature from planet_osm_polygon\n       where highway in ('residential','unclassified','pedestrian','service','footway','track','path','platform')\n          or railway in ('platform')\n       order by z_order,way_area desc) as highway_area_casing",
         "extent": "-20037508,-20037508,20037508,20037508",
         "key_field": "",
         "geometry_field": "way",
@@ -744,7 +744,7 @@
       ],
       "Datasource": {
         "type": "postgis",
-        "table": "(select way,coalesce(('highway_' || (case when highway in ('residential','unclassified','pedestrian','service','footway','cycleway','living_street','track','path','platform','services') then 'cycleway' else null end)), ('railway_' || (case when railway in ('platform') then railway else null end)), (('aeroway_' || case when aeroway in ('runway','taxiway','helipad') then aeroway else null end))) as feature from planet_osm_polygon\n       where highway in ('residential','unclassified','pedestrian','service','footway','living_street','track','path','platform','services')\n          or railway in ('platform')\n          or aeroway in ('runway','taxiway','helipad')\n       order by z_order,way_area desc) as highway_area_fill",
+        "table": "(select way,coalesce(('highway_' || (case when highway in ('residential','unclassified','pedestrian','service','footway','cycleway','living_street','track','path','platform','services') then highway else null end)), ('railway_' || (case when railway in ('platform') then railway else null end)), (('aeroway_' || case when aeroway in ('runway','taxiway','helipad') then aeroway else null end))) as feature from planet_osm_polygon\n       where highway in ('residential','unclassified','pedestrian','service','footway','living_street','track','path','platform','services')\n          or railway in ('platform')\n          or aeroway in ('runway','taxiway','helipad')\n       order by z_order,way_area desc) as highway_area_fill",
         "extent": "-20037508,-20037508,20037508,20037508",
         "key_field": "",
         "geometry_field": "way",