Keep the drill results visible

When clicking "Generate", we want to see if the drill action was
successful so we must avoid closing the window prematurely

pcbnew/dialogs/dialog_gendrill.cpp

@@ -132,6 +132,8 @@ bool DIALOG_GENDRILL::TransferDataFromWindow()
     {
         genDrillAndMapFiles( true, m_cbGenerateMap->GetValue(),
                              m_generateTentingLayers->GetValue() );
+        // Keep the window open so that the user can see the result
+        return false;
     }
     else
     {