doc: markup curl as program role

See ¹.

¹: https://www.sphinx-doc.org/en/1.5/markup/inline.html#role-program

Co-authored-by: Roberto Abdelkader Martínez Pérez <robertomartinezp@gmail.com>

docs/source/tutorial/tutorial01.rst

@@ -172,7 +172,7 @@ Backup that Database!
 
   That appears to be the case, but we better check it.
 
-  Call it with ``curl``:
+  Call it with :program:`curl`:
 
   .. code-block:: console