org.texi, orgguide.texi: Fix spelling of Sean Astin's name

* doc/org.texi: Fix a typo of Sean Astin's name as Sean Austin.

* doc/orgguide.texi: Fix a typo of Sean Astin's name as Sean Austin.

TINYCHANGE

doc/org.texi

@@ -1693,7 +1693,7 @@ In that case, all items are closed.  Here is an example:
    But in the end, no individual scenes matter but the film as a whole.
    Important actors in this film are:
    - @b{Elijah Wood} :: He plays Frodo
-   - @b{Sean Austin} :: He plays Sam, Frodo's friend.  I still remember
+   - @b{Sean Astin} :: He plays Sam, Frodo's friend.  I still remember
      him very well from his role as Mikey Walsh in @i{The Goonies}.
 @end group
 @end example

doc/orgguide.texi

@@ -503,7 +503,7 @@ blank lines.  An example:
       + I really like Miranda Otto.
    Important actors in this film are:
    - @b{Elijah Wood} :: He plays Frodo
-   - @b{Sean Austin} :: He plays Sam, Frodo's friend.
+   - @b{Sean Astin} :: He plays Sam, Frodo's friend.
 @end group
 @end smallexample