Merge pull request ocaml#12026 from Leonidas-from-XIV/debian-12-benchmark

Update benchmark Docker file to supported Debian version

Author: Alizter

bench.Dockerfile

@@ -1,4 +1,4 @@
-FROM ocaml/opam:debian-10-ocaml-4.14
+FROM ocaml/opam:debian-12-ocaml-4.14
 RUN opam depext -u patdiff.v0.15.0
 COPY --chown=opam:opam . bench-dir
 WORKDIR bench-dir