Remove 'const' from variable that may be moved

std::move on const object is ineffective, and the code will
use a performance-wise costlier SMF

Amends: 0c05d2b43ec5ab29efc3db2718289a5600da754c

Change-Id: Id4a639d9a037c3f1d79ea60faa2715075462fea1
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
(cherry picked from commit 68ae776e73881cbc160cd747e401631452e7f659)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/network/access/qhttpheaders.cpp

@@ -700,7 +700,7 @@ struct HeaderName
 
     explicit HeaderName(QAnyStringView name)
     {
-        const auto nname = normalizedName(name);
+        auto nname = normalizedName(name);
         if (auto h = HeaderName::toWellKnownHeader(nname))
             data = *h;
         else