Partially revert "Mention new strictness for &optional, &rest..."

Partially revert "Mention new strictness for &optional, &rest..."

The changes to cl argument parsing are not backwards compatible, and
cause inconvenience when writing macros (e.g., instead of doing '&aux
,@auxargs', some more complicated conditionals would be required).
The `cl-defstruct' macro makes use of this convenience when defining
empty structs (Bug#29728).
* lisp/emacs-lisp/cl-macs.el (cl--transform-lambda):
(cl--do-&aux, cl--do-arglist): Undo strict checking of &rest, &key,
and &aux.
* test/lisp/emacs-lisp/cl-macs-tests.el (cl-macs-bad-arglist): Remove
test.