Fix typo

make doc/org is failing because of syntax error.

* doc/org.texi: Fix typo

Thanks and Regards
Noorul

doc/org.texi

@@ -1327,7 +1327,7 @@ structure of these lists, many structural constructs like @code{#+BEGIN_...}
 blocks can be indented to signal that they should be considered of a list
 item.
 
-@Vindex org-list-demote-modify-bullet
+@vindex org-list-demote-modify-bullet
 If you find that using a different bullet for a sub-list (than that used for
 the current list-level) improves readability, customize the variable
 @code{org-list-demote-modify-bullet}.