Fix range-loop-detach warning in qhttp2connection.cpp

Pick-to: 6.7
Change-Id: I0b02e2f79ab7828858da3b4ca9840ad07d39a70a
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/network/access/qhttp2connection.cpp

@@ -1104,7 +1104,7 @@ void QHttp2Connection::connectionError(Http2Error errorCode, const char *message
     const auto error = qt_error(errorCode);
     auto messageView = QLatin1StringView(message);
 
-    for (QHttp2Stream *stream : m_streams) {
+    for (QHttp2Stream *stream : std::as_const(m_streams)) {
         if (stream && stream->isActive())
             stream->finishWithError(error, messageView);
     }