update test for unset showtitle attribute to be compatible with Asciidoctor 2.0.11
update test for unset showtitle attribute to be compatible with Asciidoctor 2.0.11

Hextremist/asciidoctor-pdf,dsisnero/asciidoctor-pdf,asciidoctor/asciidoctor-pdf,Hextremist/asciidoctor-pdf,mojavelinux/asciidoctor-pdf,mojavelinux/asciidoctor-pdf,dsisnero/asciidoctor-pdf,asciidoctor/asciidoctor-pdf