qhttpheaderparser: replace QBA with QBAV

in QSB expression to avoid temp allocation

Change-Id: Ib4106c5c9fa0281203dc61bad50418805c6119a9
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/network/access/qhttpheaderparser.cpp

@@ -75,7 +75,7 @@ bool QHttpHeaderParser::parseHeaders(QByteArrayView header)
             line = line.trimmed();
             if (!line.empty()) {
                 if (value.size())
-                    value += ' ' + line.toByteArray();
+                    value += ' ' + line;
                 else
                     value = line.toByteArray();
             }