Warning when byte-compiling simple.el

[Eli Zaretskii]

    In minibuffer-default-add-completions:
    simple.el:1375:15:Warning: all-completions called with 4 arguments, but
        accepts only 2-3

This warning is a lie: all-completions accepts 2 to 4 arguments.  I
don't think we should lie about that; if we want to deprecate the 4th
argument, we should find a better way of conveying this to its users.

In any case, we shouldn't call it with 4 arguments ourselves,
certainly not in such a core file as simple.el.