[Processing] Small fix in GRASS 6 provider

Author: radosuav

python/plugins/processing/algs/grass/GrassUtils.py

@@ -420,7 +420,7 @@ def grassHelpPath():
 
         if helpPath is None:
             if isWindows():
-                localPath = os.path.join(Grass7Utils.grassPath(), 'docs/html')
+                localPath = os.path.join(GrassUtils.grassPath(), 'docs/html')
                 if os.path.exists(localPath):
                     helpPath = os.path.abspath(localPath)
             elif isMac():