Don't mess up grouping in completion-all-sorted-completions

Don't mess up grouping in completion-all-sorted-completions

The default sorting order will mess up the naturally grouped order of
the candidates in the table that specified the group-function.

As seen in xref.el when

   (setq xref-show-definitions-function
         'xref-show-definitions-completing-read)
   (setq completions-group t)
   M-x fido-mode

Also partially seen with C-x 8 RET (M-x insert-char) with

   (setq read-char-by-name-sort 'code)

bug#48545

* lisp/minibuffer.el (completion-all-sorted-completions): Don't
use default sort if there's a group-function in the table.