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/git/githighlighters.cpp

@@ -138,7 +138,7 @@ void GitRebaseHighlighter::highlightBlock(const QString &text)
             setFormat(match.capturedStart(), match.capturedLength(), formatForCategory(Format_Change));
         }
     } else {
-        for (const RebaseAction &action : qAsConst(m_actions)) {
+        for (const RebaseAction &action : std::as_const(m_actions)) {
             const QRegularExpressionMatch match = action.exp.match(text);
             if (match.hasMatch()) {
                 const int len = match.capturedLength();