Bump dependency on EBNF gem to 2.0.

Author: gkellogg

rdf-turtle.gemspec

@@ -21,7 +21,7 @@ Gem::Specification.new do |gem|
   gem.required_ruby_version = '>= 2.4'
   gem.requirements          = []
   gem.add_runtime_dependency     'rdf',             '~> 3.1', '>= 3.1.2'
-  gem.add_runtime_dependency     'ebnf',            '~> 1.2'
+  gem.add_runtime_dependency     'ebnf',            '~> 2.0'
   gem.add_development_dependency 'rspec',           '~> 3.9'
   gem.add_development_dependency 'rspec-its',       '~> 1.3'
   gem.add_development_dependency 'rdf-isomorphic',  '~> 3.1'