doc(fix): correct :nodoc:

This statement was moved in b910c6a, incorrectly, and as a result the
remaining methods in the file were undocumented.

(cherry picked from commit cec3f21)

Author: flavorjones

lib/nokogiri/xml/document.rb

@@ -174,8 +174,7 @@ def empty_doc?(string_or_io)
       # Since v1.12.4
       attr_accessor :namespace_inheritance
 
-      # :nodoc:
-      def initialize(*args) # rubocop:disable Lint/MissingSuper
+      def initialize(*args) # :nodoc: # rubocop:disable Lint/MissingSuper
         @errors     = []
         @decorators = nil
         @namespace_inheritance = false