Remove unused variables in QHttp2Stream::internalSendDATA

Pick-to: 6.7
Change-Id: I13c546c7dc4cc3d15d8d92b62f053e438b5d6b64
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/network/access/qhttp2connection.cpp

@@ -316,9 +316,6 @@ void QHttp2Stream::internalSendDATA()
         return m_uploadByteDevice->readPointer(requestSize, tmp) != nullptr && tmp > 0;
     };
 
-    constexpr qint32 StackBufferSize = 4096;
-    QVarLengthArray<uchar, StackBufferSize> intermediateBuffer;
-
     bool sentEND_STREAM = false;
     while (remainingWindowSize && deviceCanRead()) {
         quint32 bytesWritten = 0;