community/racket: upgrade to 8.12
https://blog.racket-lang.org/2024/02/racket-v8-12.html
chez-musl-time_t.patch
is removed as ChezScheme no longer checks time-t-bits
: https://github.com/cisco/ChezScheme/pull/770
This change was merged into Racket with https://github.com/racket/racket/commit/d6894d31a1fc02a495cecd77ffc498d835ca5137 which is included in v8.12.