org.texi (Global and local cycling): Mention C-u C-u TAB

* org.texi (Global and local cycling): Mention C-u C-u TAB.

Thanks to François Pinard for suggesting this.

doc/org.texi

@@ -1285,6 +1285,9 @@ When @kbd{S-@key{TAB}} is called with a numeric prefix argument N, the
 CONTENTS view up to headlines of level N will be shown.  Note that inside
 tables, @kbd{S-@key{TAB}} jumps to the previous field.
 
+@cindex set startup visibility, command
+@orgcmd{C-u C-u @key{TAB},org-set-startup-visibility}
+Switch back to the startup visibility of the buffer (pxref{Initial visibility}).
 @cindex show all, command
 @orgcmd{C-u C-u C-u @key{TAB},show-all}
 Show all, including drawers.