orgguide.texi: Fix the copyright notice.

See http://orgmode.org/cgit.cgi/org-mode.git/commit/?id=cd2496
for explanations on the same change for org.texi.

doc/orgguide.texi

@@ -45,18 +45,7 @@ Copyright @copyright{} 2010-2012 Free Software Foundation
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
 any later version published by the Free Software Foundation; with no
-Invariant Sections, with the Front-Cover texts being ``A GNU Manual,''
-and with the Back-Cover Texts as in (a) below.  A copy of the license
-is included in the section entitled ``GNU Free Documentation License.''
-
-(a) The FSF's Back-Cover Text is: ``You have the freedom to copy and
-modify this GNU manual.  Buying copies from the FSF supports it in
-developing GNU and promoting software freedom.''
-
-This document is part of a collection distributed under the GNU Free
-Documentation License.  If you want to distribute this document
-separately from the collection, you can do so by adding a copy of the
-license to the document, as described in section 6 of the license.
+Invariant Sections and no Cover Texts.
 @end quotation
 @end copying