Revert "drop non-existing slot"

This reverts commit 4126b5fa096383e1c561512097e51e10bcf8de79.

src/plugins/wfs/qgswfssourceselect.h

@@ -65,6 +65,7 @@ class QgsWFSSourceSelect: public QDialog, private Ui::QgsWFSSourceSelectBase
     void changeCRSFilter();
     void on_cmbConnections_activated( int index );
     void capabilitiesReplyFinished();
+    void capabilitiesReplyProgress( qint64, qint64 );
     void on_btnSave_clicked();
     void on_btnLoad_clicked();