Update ebnf dependency to 2.3.

Author: gkellogg

rdf-turtle.gemspec

@@ -21,7 +21,7 @@ Gem::Specification.new do |gem|
   gem.required_ruby_version = '>= 2.6'
   gem.requirements          = []
   gem.add_runtime_dependency     'rdf',             '~> 3.2'
-  gem.add_runtime_dependency     'ebnf',            '~> 2.2'
+  gem.add_runtime_dependency     'ebnf',            '~> 2.3'
   gem.add_development_dependency 'erubis',          '~> 2.7'
   gem.add_development_dependency 'htmlentities',    '~> 4.3'
   gem.add_development_dependency 'rspec',           '~> 3.10'