Fix menu entries: Move Subtree Up/Down

* lisp/org.el (org-org-menu): Fix entries.

`org-shiftmetaup' and `org-shiftmetadown' only drag a single line up
or down.  They are not about structure editing.

Reported-by: James Harkins <jamshark70@qq.com>
<http://permalink.gmane.org/gmane.emacs.orgmode/92299>

lisp/org.el

@@ -21293,8 +21293,8 @@ on context.  See the individual commands for more information."
     ("Edit Structure"
      ["Refile Subtree" org-refile (org-in-subtree-not-table-p)]
      "--"
-     ["Move Subtree Up" org-shiftmetaup (org-in-subtree-not-table-p)]
-     ["Move Subtree Down" org-shiftmetadown (org-in-subtree-not-table-p)]
+     ["Move Subtree Up" org-metaup (org-at-heading-p)]
+     ["Move Subtree Down" org-metadown (org-at-heading-p)]
      "--"
      ["Copy Subtree"  org-copy-special (org-in-subtree-not-table-p)]
      ["Cut Subtree"  org-cut-special (org-in-subtree-not-table-p)]