[Orgmode] small typo in docstring of org-beamer.el (herder -> header)

[Stephen Eglen]

git diff lisp/org-beamer.el
diff --git a/lisp/org-beamer.el b/lisp/org-beamer.el
index 2631e70..49b3499 100644
--- a/lisp/org-beamer.el
+++ b/lisp/org-beamer.el
@@ -382,7 +382,7 @@ The need to be after the begin statement of the 
environment."
              (insert dovl)))))))
 
 (defun org-beamer-amend-header ()
-  "Add `org-beamer-header-extra' to the LaTeX herder.
+  "Add `org-beamer-header-extra' to the LaTeX header.
 If the file contains the string BEAMER-HEADER-EXTRA-HERE on a line
 by itself, it will be replaced with `org-beamer-header-extra'.  If not,
 the value will be inserted right after the documentclass statement."