Simplify method to check an image max size

We were converting megabytes to bytes with the `megabytes` method and
then adding a `bytes_to_megabytes` method to convert it back to bytes,
which is the same as not doing anything at all :).

app/helpers/imageables_helper.rb

@@ -4,11 +4,7 @@ module ImageablesHelper
   end
 
   def imageable_max_file_size
-    bytes_to_megabytes(Setting["uploads.images.max_size"].to_i.megabytes)
-  end
-
-  def bytes_to_megabytes(bytes)
-    bytes / Numeric::MEGABYTE
+    Setting["uploads.images.max_size"].to_i
   end
 
   def imageable_accepted_content_types