Port from qAsConst() to std::as_const()

We've been requiring C++17 since Qt 6.0, and our qAsConst use finally
starts to bother us (QTBUG-99313), so time to port away from it
now.

Since qAsConst has exactly the same semantics as std::as_const (down
to rvalue treatment, constexpr'ness and noexcept'ness), there's really
nothing more to it than a global search-and-replace.

Task-number: QTBUG-99313
Change-Id: I88edd91395849574436299b8badda21bb93bea39
Reviewed-by: hjk <hjk@qt.io>

src/plugins/todo/optionsdialog.cpp

@@ -198,7 +198,7 @@ void OptionsDialog::setSettings(const Settings &settings)
     m_scanInSubprojectRadioButton->setChecked(settings.scanningScope == ScanningScopeSubProject);
 
     m_keywordsList->clear();
-    for (const Keyword &keyword : qAsConst(settings.keywords))
+    for (const Keyword &keyword : std::as_const(settings.keywords))
         addToKeywordsList(keyword);
 }