fixed example

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@32995 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.category/r.category.html

@@ -156,7 +156,7 @@ values in the output.
 <dl>
 <dt>Example defining category labels:
 <dd><div class="code"><pre>
-r.category thresh_gt0_lst_${YEAR}${MONTH}_avg_filt cats=1 rules=- << EOF
+r.category diseasemap rules=- << EOF
 1:potential absence
 2:potential presence
 EOF