Be consistent checking changes in draft versions

There's no reason to only convert Markdown to HTML in translations when
their body changes but to always convert it when the "main" body field
changes.

Whether we should always use the condition or never use it is something
we can debate about, though.

app/models/legislation/draft_version.rb

@@ -26,8 +26,10 @@ class Legislation::DraftVersion < ActiveRecord::Base
     renderer = Redcarpet::Render::HTML.new(with_toc_data: true)
     toc_renderer = Redcarpet::Render::HTML_TOC.new(with_toc_data: true)
 
-    self.body_html = Redcarpet::Markdown.new(renderer).render(body)
-    self.toc_html = Redcarpet::Markdown.new(toc_renderer).render(body)
+    if body_changed?
+      self.body_html = Redcarpet::Markdown.new(renderer).render(body)
+      self.toc_html = Redcarpet::Markdown.new(toc_renderer).render(body)
+    end
 
     translations.each do |translation|
       if translation.body_changed?