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/syntaxhighlighter.cpp

@@ -819,7 +819,7 @@ void SyntaxHighlighterPrivate::updateFormats(const FontSettings &fontSettings)
     this->fontSettings = fontSettings;
     // C_TEXT is handled by text editor's foreground and background color,
     // so use empty format for that
-    for (const auto &pair : qAsConst(formatCategories)) {
+    for (const auto &pair : std::as_const(formatCategories)) {
         formats[pair.first] = pair.second == C_TEXT ? QTextCharFormat()
                                                     : fontSettings.toTextCharFormat(pair.second);
     }