r.horizon manual: fix nasty non-ASCII char

fixes a8aa37c9beb23db4c068b6d318b3a3ec30bdcded

raster/r.horizon/r.horizon.html

@@ -134,7 +134,7 @@ actually are. It also accounts for the changes of angles towards
 cardinal directions caused by the projection (see above). 
 
 <p>
-The output with the <b>-d</b> flag is azimuth degree (-90 – 90, where
+The output with the <b>-d</b> flag is azimuth degree (-90 to 90, where
 0 is parallel with the focal cell). In case of negative horizon values
 obtained this indicates that the horizon height is below the cell it is
 computed from.