Move org-timestamp-formats setting to the :config block of Org

This variable is actually a const so it shouldn’t be tampered with (as yantar92 said in [a Matrix
message](https://matrix.to/#/%21rUhEinythPhVTdddsb%3Amatrix.org/%2417625298361396UYIZz%3Amatrix.org?via=matrix.org&via=envs.net&via=fedora.im),
but this specific value [should be
OK](https://matrix.to/#/%21rUhEinythPhVTdddsb%3Amatrix.org/%2417625298651398YcFjt%3Amatrix.org?via=matrix.org&via=envs.net&via=fedora.im).

init.el

@@ -926,7 +926,6 @@ order."
    'append)
   (setq-default org-default-notes-file (expand-file-name "notes.org" org-directory)
                 org-agenda-files `(,org-directory)
-                org-time-stamp-formats '("<%Y-%m-%d>" . "<%Y-%m-%d %H:%M>")
                 org-todo-keywords '((sequence "TODO(t)"
                                               "DOING(w@/!)"
                                               "BLOCKED(b@/!)"
@@ -943,6 +942,7 @@ order."
                            (off . "<span class=\"task-todo\">☐</span>")
                            (trans . "<span class=\"task-in-progress\">▣</span>"))))
   :config
+  (setq org-timestamp-formats (cons "%Y-%m-%d" "%Y-%m-%d %H:%M"))
   ;; Load the markdown exporter
   (require 'ox-md)
   ;; Handle org-protocol:// links