r.drain manual: fix typo (thanks to Bas Couwenberg), fixes https://trac.osgeo.org/grass/ticket/3484

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@72161 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.drain/r.drain.html

@@ -33,7 +33,7 @@ incompatible.
 
 <p>For an elevation surface, the path is calculated by choosing the
 steeper "slope" between adjacent cells. The slope calculation
-accurately acounts for the variable scale in lat-lon projections. For
+accurately accounts for the variable scale in lat-lon projections. For
 a cost surface, the path is calculated by following the movement
 direction surface back to the start point given
 in <em><a href="r.walk.html">r.walk</a></em> or