Backport commit 9a4862a97 from Emacs

doc/misc/org.org: Remove spurious markup.
9a4862a9738c2abab8fb4fb2e4e57b69dea679d7
Stefan Kangas
Wed Jun 8 13:16:32 2022 +0200

doc/org-manual.org

@@ -12442,7 +12442,7 @@ should in principle be exportable as a Beamer presentation.
   When =ignoreheading= is set, Org export ignores the entry's headline
   but not its content.  This is useful for inserting content between
   frames.  It is also useful for properly closing a =column=
-  environment.  @end itemize
+  environment.
 
   #+cindex: @samp{BEAMER_ACT}, property
   #+cindex: @samp{BEAMER_OPT}, property