QmlDebug: Drop unimplemented private method

Change-Id: I66a2212e6d2eb2208444ca97c64b10ac50c57c43
Reviewed-by: hjk <hjk@qt.io>

src/libs/qmldebug/qpacketprotocol.h

@@ -66,7 +66,6 @@ public:
     QByteArray data() const;
 
 private:
-    void init(QIODevice::OpenMode mode);
     QBuffer buf;
 };