g.gui.tplot: replace copied code with existing function

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@69248 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/tplot/frame.py

@@ -133,9 +133,7 @@ class TplotFrame(wx.Frame):
         if self._giface.GetMapDisplay():
             self.coorval.OnClose()
             self.cats.OnClose()
-        if self.dbif.connected is True:
-            self.dbif.close()
-        tgis.stop_subprocesses()
+        self.__del__()
         self.Destroy()
 
     def _layout(self):