Fix Qt deprecation warn for QList::fromSet()

Fix Qt deprecation warn for QList::fromSet()

Fix the following warning from Qt 5.14.1:

  error: ‘static QList<T> QList<T>::fromSet(const QSet<T>&) [with T = QString]’ is deprecated: Use QList<T>(set.begin(), set.end()) instead. [-Werror=deprecated-declarations]

Regarding QList::fromSet(), the documentation now states the
following [1]:

  Since Qt 5.14, range constructors are available for Qt's generic
  container classes and should be used in place of this method.

[1] https://doc.qt.io/qt-5/qlist.html