Upgrade asciidoctor and its jruby dependency
Upgrade asciidoctor and its jruby dependency

That version of asciidoctor fixes an ArrayIndexOutOfBoundsException in
AsciidoctorUtils.getOptions() under certain circumstances, amongst other
fixes.

Change-Id: Ia1b818e85badfb43187f1080e9392fa50984b7c3

GerritCodeReview/plugins_x-docs,GerritCodeReview/plugins_x-docs