deps: Update go-org to v1.4.0

- Add support for pretty urls [1]. Rewrite file links:
  1. replace the `.org` extension with `/` (`/foo.org` -> `/foo/`)
  2. prefix unrooted links with `../` as relative links start in the fake
  subdirectory `/foo/` rather than `/`
- Fix case-sensitivity of org drawer `🔚`

[1] https://gohugo.io/content-management/urls/#pretty-urls

markup/org/convert.go

@@ -52,6 +52,7 @@ func (c *orgConverter) Convert(ctx converter.RenderContext) (converter.Result, e
 		return afero.ReadFile(c.cfg.ContentFs, filename)
 	}
 	writer := org.NewHTMLWriter()
+	writer.PrettyRelativeLinks = !c.cfg.Cfg.GetBool("uglyURLs")
 	writer.HighlightCodeBlock = func(source, lang string, inline bool) string {
 		highlightedSource, err := c.cfg.Highlight(source, lang, "")
 		if err != nil {