Fix bug in vocabulary writer with %() strings.

Author: gkellogg

lib/rdf/vocab/writer.rb

@@ -263,7 +263,7 @@ def from_node(name, attributes, term_type)
 
       def serialize_value(value, key, indent: "")
         if value.is_a?(Literal) && %w(: comment definition notation note editorialNote).include?(key.to_s)
-          "%(#{value.to_s.gsub('(', '\(').gsub(')', '\)')}).freeze"
+          "#{value.to_s.inspect}.freeze"
         elsif value.is_a?(RDF::URI)
           "#{value.pname.inspect}.freeze"
         elsif value.is_a?(RDF::Vocabulary::Term)