sage

e33c041b -

gh-36359: a few details in combinat (designs) Cleaning up a few files in combinat/designs, in particular about missing empty lines. ### :memo: Checklist - [x] The title is concise, informative, and self-explanatory. - [x] The description explains in detail what this PR is about. URL: https://github.com/sagemath/sage/pull/36359 Reported by: Frédéric Chapoton Reviewer(s): David Coudert, Frédéric Chapoton