Fix missing signal/slot connection resulting in non-woring autocompleter for value relation fields (fixes #16676). (#5821)

Backported from d7b08c7

Author: kervel

src/gui/editorwidgets/qgsvaluerelationwidgetwrapper.cpp

@@ -150,6 +150,8 @@ void QgsValueRelationWidgetWrapper::initWidget( QWidget* editor )
     QCompleter* completer = new QCompleter( m, mLineEdit );
     completer->setCaseSensitivity( Qt::CaseInsensitive );
     mLineEdit->setCompleter( completer );
+
+    connect( mLineEdit, SIGNAL( textChanged( QString ) ), this, SLOT( onValueChanged() ) );
   }
 }