tls-gnutls.c: Revert the option change in gnutls_bye

Revert to the code from PR #365, because some TLS 1.2 implementations (e.g. Windows Server 2022) do not follow the standard properly, and sticking to standard would cause 20s-30s delays in printing over TLS.

With this change, both our TLS implementations behave the same - OpenSSL uses this option by default and it is not possible to change it, while GNUTLS provides this option to configure the closing behavior.

Author: zdohnal

cups/tls-gnutls.c

@@ -1992,7 +1992,7 @@ _httpTLSStop(http_t *http)		// I - Connection to server
   int	error;				// Error code
 
 
-  error = gnutls_bye(http->tls, http->mode == _HTTP_MODE_CLIENT ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
+  error = gnutls_bye(http->tls, GNUTLS_SHUT_WR);
   if (error != GNUTLS_E_SUCCESS)
     _cupsSetError(IPP_STATUS_ERROR_INTERNAL, gnutls_strerror(errno), 0);