[declare] Fix types of mutual lemmas when using Admitted.

We fix a clear coding mistake in
79bcf1c0a22e736c4e2cae3460c35b3d9fca9aa0 that forgot to update the
type of the parameter entry when saving mutual definitions without a
body.

We follow the solution suggested by Hugo Herbelin and drop the
type used in `start_proof`. Note the duplication here indeed.

Fixes #12895

Co-authored-by: Hugo Herbelin <Hugo.Herbelin@inria.fr>

0 files changed, 0 insertions, 0 deletions