Documentation: asciidoc.conf: fix verse block with block titles

Documentation: asciidoc.conf: fix verse block with block titles

No files use the variant of block-title with verse-block, but
such a case would have generated broken docbook XML (<simpara> is
not allowed inside <para>). This fixes the potential deviation from
valid docbook XML.

Testing done with asciidoc 8.3.1 and docbook-xsl 1.74.0.

Signed-off-by: Chris Johnsen <chris_johnsen@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>