Update elfeed-enclosure-default-dir doc string

[Bargraph6]

The docstring for the elfeed-enclosure-default-dir variable mentions being able to set this to a function.

When I tried to do this with a lambda, or with the following example code, I got errors when trying to download an enclosure:

read-file-name: Wrong type argument: stringp, my-elfeed-enclosure-dir

Reading the code in elfeed-show.el, it looks like it only expects a string. However, my elisp is very weak, so I may just be making an obvious mistake here?¹

example code

(defun my-elfeed-enclosure-dir (fname mime-type)
  "Return the directory for saving enclosures based on filename and mime-type."

  (mkdir "/home/my-user/elfeed/" t)
  "/home/my-user/elfeed/")

(setq elfeed-enclosure-default-dir #'my-elfeed-enclosure-dir)

Footnotes

1. I did a search on github and didn't see anyone else setting this as a function ↩