QNetworkReply::errorString() returns untranslated strings

The QHttpNetworkConnectionPrivate::errorDetail is supposed to return a translated string, which is then set as the QNetworkReply error. The current code incorrectly uses QT_TRANSLATE_NOOP, which mark the strings for translation, but does not translate them. The result is that even with a translator loaded those strings are written in English.

The attached patch fixes it. I did not do a MR because it's a trivial bug, but writing an test for it requires setting up the network autotest environment...