v.colors: update manual (rast -> raster)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@63702 15284696-431f-4ddb-bdfa-cd5b030d7da7

vector/v.colors/v.colors.html

@@ -10,7 +10,7 @@ by <b>column</b> option. For 3D vector maps is allowed to define color
 rules based on points or centroids z-coordinate (<b>use=z</b>). 3D
 vector lines are not supported.
 
-<p>The <b>rast</b> option allows user to specify a raster map from
+<p>The <b>raster</b> option allows user to specify a raster map from
 which to copy the color table, similarly <b>volume</b> option for 3D
 raster map.