Re-enable hiding LaTeX

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>

convert.rb

@@ -68,13 +68,12 @@ files.each do |file|
     t.replace(rendered)
   end
 
+  found_any ||= document.at('meta[name="needs-latex"]')
+
   # If we didn't find any mathematical equations, no need to include KaTeX CSS.
-  # Disabled here because Bergamot technically doesn't require math blocks
-  # on the page but does need the CSS.
-  #
-  # unless found_any
-  #   document.css('link[href$="katex.css"], link[href$="katex.min.css"]').each(&:remove)
-  # end
+  unless found_any
+    document.css('link[href$="katex.css"], link[href$="katex.min.css"]').each(&:remove)
+  end
 
   File.write(file, document.to_html(encoding: 'UTF-8'))
 end