Documentation: Various syntax fixes and text improvements

Documentation: Various syntax fixes and text improvements

This started as a fix for OpenVPN/openvpn#606 but while
reviewing the documentation referenced from there I
identified more and more issues.

There a few classes of changes in here:
- Fix wrong `...` syntax, which makes no sense in rst.
- Remove some very old references to OpenVPN v1 behavior.
- Fix typos or other small text issues.

Note: The usage of ``...`` vs :code:`...` is very
inconsistent, but fixing that is outside of the scope
of this patch. I have tried to make it at least
locally consistent.

Github: Fixes OpenVPN/openvpn#606
Change-Id: Iee535f1502ab3dcb7bde7f2593c2e122d27d9189
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1414
Message-Id: <20251208114224.10223-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg34878.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>