fix range-loop-construct warnings

[Vedingrot]

Costly copying of QString on each for cycle iteration should be avoided.

warning:

src/mapmanagerfeature.cpp: In member function 'MapManager::FeatureValhalla::PackStateType MapManager::FeatureValhalla::getPackState(QString, QString, QString) const':
src/mapmanagerfeature.cpp:558:26: warning: loop variable 'tilename' creates a copy from type 'const QString' [-Wrange-loop-construct]
  558 |       for (const QString tilename: tiles)
      |                          ^~~~~~~~
src/mapmanagerfeature.cpp:558:26: note: use reference type to prevent copying
  558 |       for (const QString tilename: tiles)
      |                          ^~~~~~~~
      |                          &
src/mapmanagerfeature.cpp: In member function 'virtual void MapManager::FeatureValhalla::fillWantedFiles(const QJsonObject&, QSet<QString>&)':
src/mapmanagerfeature.cpp:656:26: warning: loop variable 'tilename' creates a copy from type 'const QString' [-Wrange-loop-construct]
  656 |       for (const QString tilename: tiles)
      |                          ^~~~~~~~
src/mapmanagerfeature.cpp:656:26: note: use reference type to prevent copying
  656 |       for (const QString tilename: tiles)
      |                          ^~~~~~~~
      |                          &