Remove HttpGet::error() function.

This function returns an internal enum value of QHttp (which is also
deprecated). It was only used for showing an error to the user / showing it in
the system trace. Since it is an enum value it doesn't have much value. Log /
show the error string instead.

Change-Id: I54b9b6026969f8108f779b02a04477f0ad9201ab

rbutil/rbutilqt/base/bootloaderinstallbase.cpp

@@ -80,7 +80,7 @@ void BootloaderInstallBase::downloadBlFinish(bool error)
     }
     if(error) {
         emit logItem(tr("Download error: %1")
-                .arg(m_http.error()), LOGERROR);
+                .arg(m_http.errorString()), LOGERROR);
         emit done(true);
         return;
     }