Delete reference to obsolete library complete.el

* doc/misc/tramp.texi (Frequently Asked Questions): Delete reference
to obsolete library complete.el.

doc/misc/tramp.texi

@@ -4986,14 +4986,6 @@ minibuffer:
   (expand-abbrev))
 @end group
 
-@group
-;; If you use partial-completion-mode
-(defadvice PC-do-completion
-  (before my-PC-do-completion activate)
-  (expand-abbrev))
-@end group
-@end lisp
-
 The reduced typing: @kbd{C-x C-f xy @key{TAB}}.
 
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