* lisp/tab-bar.el: Improve tab-bar-auto-width-predicate-default (bug#71883).

* lisp/tab-bar.el: Improve tab-bar-auto-width-predicate-default (bug#71883).

(tab-bar--auto-width-faces-default): New variable with the
value from the default value of tab-bar-auto-width-faces.
(tab-bar-auto-width-faces): Set the default value to
tab-bar--auto-width-faces-default.
(tab-bar-auto-width-predicate-default): For backwards-compatibility
use the old logic of checking tab-bar-auto-width-faces when its value
was changed.  Otherwise, check for a symbol, but remove "current-group"
from the list of symbols.

(cherry picked from commit 60da504cf7ca2c95ab4e3bea10875271b15a5a45)