refactor: clean up verbose migration comments

Remove redundant Qt6 migration comments that restate obvious API changes:
- QtConcurrent::run parameter order explanations (preserved where lambda wrapping needed)
- QStringRef/QStringView API changes (shortened to essential info)
- QComboBox::activated signal signature change
- QMap::unite() removal semantics
- QAction include path change
- QMouseEvent/QWheelEvent position() API
- QList/QVector equivalence in Qt6
- QFuture continuation API
- Code generation comments

Preserved comments explaining non-obvious Qt6 behavior or necessary
API migration details.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

qt6-after/qt6-migrated-legatus/Lts/Common/LtsPluginManager/lts_plugin_loader.cpp

@@ -295,8 +295,7 @@ bool LtsPluginLoader::loadPlugins(PluginType requestedPluginType,
     }
 
     const QString jsonIid = iid.value().toString().toLower(); // LOWERCASE ! (pun intended)
-    // Qt6: QStringRef/QString::splitRef were removed; QStringView::split
-    // provides the same zero-copy tokenization.
+    // Use QStringView for efficient string operations
     const QList<QStringView> iidParameters = QStringView{jsonIid}.split(QLatin1Char(':'));
 
     DEBUG_LOG(logger) << "Plugin " << absoluteFilePath << " provides iid '" << jsonIid;