v.colors: avoid unix commands (head) in the manual

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@63701 15284696-431f-4ddb-bdfa-cd5b030d7da7

vector/v.colors/v.colors.html

@@ -65,7 +65,7 @@ instead of creating color table.
 v.colors map=soils_general layer=1 color=wave use=attr column=AREA rgb_column=GRASSRGB
 
 # See some GRASSRGB values:
-v.db.select map=soils_general | head -n 4
+v.db.select map=soils_general where="cat < 4"
 cat|OBJECTID|AREA|PERIMETER|GSLNC250_|GSLNC250_I|GSL_NAME|GRASSRGB
 1|1|0|164616.125|2|1|NC113|212:42:127
 2|2|0|30785.529297|3|2|NC096|212:42:127