[3.13] gh-118772: Allow TypeVars without a default to follow those with a default when constructing aliases (GH-118774) (#118776)

(cherry picked from commit aac6b019fe91e2f9f7a955d4fc4db5d5efd968c9)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>