Docs: Fix typo in table description (#664)

Add "default" to the docs for the Yoshida Butcher Table constant
description.

doc/arkode/guide/source/Butcher.rst

@@ -2283,7 +2283,7 @@ and the default 5th order method.
 Accessible via the constant (or string) ``ARKODE_SPRK_YOSHIDA_6_8`` to
 :c:func:`ARKodeSPRKTable_Load` or :c:func:`ARKodeSPRKTable_LoadByName`.
 This is the 6th order method given by Yoshida in :cite:p:`Yoshida:90`
-and the 6th order method.
+and the default 6th order method.
 
 
 .. c:enumerator:: ARKODE_SPRK_SUZUKI_UMENO_8_16