[Emacs] Put use-package around custom org-export-get-reference

This prevents it from getting clobbered when org-export is loaded.

dotfiles/emacs.d/README.org

@@ -3111,7 +3111,10 @@ as its link target.
 This function replaces the default naming scheme with a call to
 ~imalison:generate-name~, and uses a slightly different uniquify approach.
 #+BEGIN_SRC emacs-lisp
-(defun org-export-get-reference (datum info)
+(use-package org-export
+  :ensure nil
+  :config
+  (defun org-export-get-reference (datum info)
     "Return a unique reference for DATUM, as a string.
 DATUM is either an element or an object.  INFO is the current
 export state, as a plist.  Returned reference consists of
@@ -3131,7 +3134,7 @@ alphanumeric characters only."
                  (new-name (format "%s%s" name (if (< 0 number) number ""))))
             (puthash name number reverse-cache)
             (puthash datum new-name cache)
-          new-name))))
+            new-name)))))
 #+END_SRC
 **** org-projectile
  #+BEGIN_SRC emacs-lisp