Remove TEST_GET_DEFAULT_GATEWAY as it duplicates --show-gateway

Remove TEST_GET_DEFAULT_GATEWAY as it duplicates --show-gateway

This debug code is not very useful as it is outdated and the same
functionality is provided by --show-gateway

Change-Id: Ie7fd59cc84e2eb024086c28c2ec2a5606a2b2e7c
Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20231201111717.14940-1-frank@lichtenheld.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg27624.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>