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/texteditor/fontsettingspage.cpp

@@ -702,7 +702,7 @@ void FontSettingsPageWidget::refreshColorSchemeList()
 
     int selected = 0;
 
-    for (const FilePath &file : qAsConst(schemeList)) {
+    for (const FilePath &file : std::as_const(schemeList)) {
         if (m_value.colorSchemeFileName() == file)
             selected = colorSchemes.size();
         colorSchemes.append(ColorSchemeEntry(file, true));