minor docs fix

Author: karussell

docs/core/custom-models.md

@@ -98,7 +98,7 @@ There are also some that take on a numeric value, like:
 
 - average_slope: a number for 100 * "elevation change" / edge_distance for a road segment; it changes the sign in reverse direction; see max_slope
 - curvature: "beeline distance" / edge_distance (0..1) e.g. a curvy road is smaller than 1
-- hike_rating: a number from 0 to 6 for the `sac_scale` in OSM, e.g. 0 means "missing", 1 means "hiking", 2 means "mountain_hiking", 3 means demanding_mountain_hiking, 4 means alpine_hiking, 5 means demanding_alpine_hiking, and 5 means difficult_alpine_hiking
+- hike_rating: a number from 0 to 6 for the `sac_scale` in OSM, e.g. 0 means "missing", 1 means "hiking", 2 means "mountain_hiking", 3 means demanding_mountain_hiking, 4 means alpine_hiking, 5 means demanding_alpine_hiking, and 6 means difficult_alpine_hiking
 - mtb_rating: a number from 0 to 7 for the `mtb:scale` in OSM, e.g. 0 means "missing", 1 means `mtb:scale=0`, 2 means `mtb:scale=1` and so on. A leading "+" or "-" character is ignored.  
 - horse_rating: a number from 0 to 6 for the `horse_scale` in OSM, e.g. 0 means "missing", 1 means "common", 2 means "demanding", 3 means difficult, 4 means critical, 5 means dangerous, and 6 means impossible
 - lanes: number of lanes