build(deps): bump ocaml/setup-ocaml from 2 to 3

Bumps [ocaml/setup-ocaml](https://github.com/ocaml/setup-ocaml) from 2 to 3.
- [Release notes](https://github.com/ocaml/setup-ocaml/releases)
- [Changelog](https://github.com/ocaml/setup-ocaml/blob/master/CHANGELOG.md)
- [Commits](ocaml/setup-ocaml@v2...v3)

---
updated-dependencies:
- dependency-name: ocaml/setup-ocaml
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/validate.yml

@@ -67,7 +67,7 @@ jobs:
         with:
           deno-version: v1.x
       - uses: taiki-e/install-action@just
-      - uses: ocaml/setup-ocaml@v2
+      - uses: ocaml/setup-ocaml@v3
         with:
           ocaml-compiler: "5.1"
       - uses: actions/setup-java@v4