Add org-tempo to org-modules instead of requiring it

I think requiring it broke at some point? This new method seems more
correct anyway

.emacs.d/init.el

@@ -202,7 +202,7 @@
                             ("M-N" . org-metadown))
          :map org-src-mode-map ("C-z" . org-src-export-to-pdf))
   :config
-  (use-package org-tempo :demand) ; enable org-tempo templates
+  (add-to-list 'org-modules 'org-tempo t) ; enable org-tempo templates
 
   ;; Make windmove work in org-mode:
   (add-hook 'org-shiftup-final-hook 'windmove-up)