Remove use of 'dh dh2048.pem' from sample configs, remove 'dh2048.pem' file

Remove use of 'dh dh2048.pem' from sample configs, remove 'dh2048.pem' file

Since commit bd9aa06feb41 (Jan 2015) OpenVPN has allowed to use
'--dh none' to disable traditional Diffie Hellman, since more secure
ECDH algorithms are available that do not use explicit DH parameters.

If configured with a suffiently high securelevel (3+), or if running in
FIPS mode, OpenSSL 3.5 will refuse 2048 bit DH files, making our tests
fail.

Thus, remove all the DH2048 stuff from our sample configs.

Github: triggered by OpenVPN/openvpn#819

Change-Id: If66438662bd862a195b2a69c4fa45f63838982b7
Signed-off-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20250820175459.11227-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg32632.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>