[ruby/rdoc] Remove code for versions older than Ruby 2.3

https://github.com/ruby/rdoc/commit/a61b777df0

lib/rdoc/comment.rb

@@ -133,12 +133,7 @@ class RDoc::Comment
   # HACK dubious
 
   def encode! encoding
-    # TODO: Remove this condition after Ruby 2.2 EOL
+    @text = String.new @text, encoding: encoding
-    if RUBY_VERSION < '2.3.0'
-      @text = @text.force_encoding encoding
-    else
-      @text = String.new @text, encoding: encoding
-    end
     self
   end
 

lib/rdoc/encoding.rb

@@ -124,12 +124,7 @@ module RDoc::Encoding
     if text.kind_of? RDoc::Comment
       text.encode! encoding
     else
-      # TODO: Remove this condition after Ruby 2.2 EOL
+      String.new text, encoding: encoding
-      if RUBY_VERSION < '2.3.0'
-        text.force_encoding encoding
-      else
-        String.new text, encoding: encoding
-      end
     end
   end