Fix #7969, 'layer source' in vector properties is empty

- Revert part of 6c51965, where setting the line edit field was (accidentally?) removed

Author: dakcarto

src/app/qgsvectorlayerproperties.cpp

@@ -342,6 +342,7 @@ void QgsVectorLayerProperties::syncToLayer( void )
   // populate the general information
   mLayerOrigNameLineEdit->setText( layer->originalName() );
   txtDisplayName->setText( layer->name() );
+  txtLayerSource->setText( layer->publicSource() );
   pbnQueryBuilder->setWhatsThis( tr( "This button opens the query "
                                      "builder and allows you to create a subset of features to display on "
                                      "the map canvas rather than displaying all features in the layer" ) );