docs: correct formatting errors in xmdomain.cfg

docs: correct formatting errors in xmdomain.cfg

This patch corrects the following errors produced by pod2man:

Hey! The above document had some coding errors, which are explained
below:

Around line 301:
    You can't have =items (as at line 305) unless the first thing after
    the =over is an =item

Around line 311:
    '=item' outside of any '=over'

Signed-off-by: Matt Wilson <msw@amazon.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>