doc: fix indentation in protocol-options.rst

doc: fix indentation in protocol-options.rst

The bullet points are not proeprly indented and they trigger
the following error/warning:

rst2man.py openvpn.8.rst > openvpn.8
man-sections/protocol-options.rst:62: (ERROR/3) Unexpected indentation.
man-sections/protocol-options.rst:67: (WARNING/2) Block quote ends without
a blank line; unexpected unindent.
rst2man.py openvpn-examples.5.rst > openvpn-examples.5
rst2html.py openvpn.8.rst > openvpn.8.html
man-sections/protocol-options.rst:62: (ERROR/3) Unexpected indentation.
man-sections/protocol-options.rst:67: (WARNING/2) Block quote ends without
a blank line; unexpected unindent.

Fix indentation and add white lines as expected.

Signed-off-by: Antonio Quartulli <a@unstable.cc>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20210921121519.18912-1-a@unstable.cc>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg22867.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>