Merge pull request #1636 from progit/dependabot/bundler/asciidoctor-2.0.13

Update asciidoctor requirement from 2.0.12 to 2.0.13

Author: ben

Gemfile

@@ -1,7 +1,7 @@
 source 'https://rubygems.org'
 
 gem 'rake', '13.0.3'
-gem 'asciidoctor', '2.0.12'
+gem 'asciidoctor', '2.0.13'
 
 gem 'json', '2.5.1'
 gem 'awesome_print', '1.9.2'