org.el: Fix `org-indent-region' bug in source block

* lisp/org.el (org-indent-region): Use `save-window-excursion'
to restore point after indenting region in source blocks.

Thanks to Gustavo Barros for reporting this bug.

lisp/org.el

@@ -19280,7 +19280,7 @@ indent.  The function will not indent contents of example blocks,
 verse blocks and export blocks as leading white spaces are
 assumed to be significant there."
   (interactive "r")
-  (save-excursion
+  (save-window-excursion
     (goto-char start)
     (skip-chars-forward " \r\t\n")
     (unless (eobp) (beginning-of-line))