Mark QHttpNetworkConnectionChannel as final

To suppress clang-tidy's
bugprone-pointer-arithmetic-on-polymorphic-object
because we store a dynamically allocated array of
QHttpNetworkConnectionChannel objects in QHttpNetworkConnectionPrivate
and index into this all over the code.

Pick-to: 6.9 6.8
Change-Id: Ibcdf7c8acc4a57eaf36bca3719733655053ac818
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Mate Barany <mate.barany@qt.io>

src/network/access/qhttpnetworkconnectionchannel_p.h

@@ -62,7 +62,7 @@ class QByteArray;
 typedef std::pair<QHttpNetworkRequest, QHttpNetworkReply*> HttpMessagePair;
 #endif
 
-class QHttpNetworkConnectionChannel : public QObject {
+class QHttpNetworkConnectionChannel final : public QObject {
     Q_OBJECT
 public:
     // TODO: Refactor this to add an EncryptingState (and remove pendingEncrypt).