fix confusing terminology (backport from 64)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@39947 15284696-431f-4ddb-bdfa-cd5b030d7da7

vector/vectorintro.html

@@ -100,7 +100,7 @@ approximation and topographic analysis from a point or isoline file.
 <li> volume: a 3D corpus, the topological composition of faces and kernel (not yet implemented). </li>
 </ul>
 <p>
-Note that all lines and boundaries can be polylines (with nodes in between).
+Note that all lines and boundaries can be polylines (with vertices in between).
 <p>
 Area topology also holds information about isles. These isles are located
 within that area, not touching the boundaries of the outer area. Isles