t.rast.out.vtk: fixed wrong parameter name

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@63190 15284696-431f-4ddb-bdfa-cd5b030d7da7

temporal/t.rast.out.vtk/t.rast.out.vtk.py

@@ -77,7 +77,7 @@ def main():
     # Get the options
     input = options["input"]
     elevation = options["elevation"]
-    expdir = options["expdir"]
+    expdir = options["directory"]
     where = options["where"]
     null = options["null"]
     use_pdata = flags["p"]