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/build-test.yml

@@ -23,7 +23,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Use OCaml ${{ matrix.ocaml-version }}
-        uses: ocaml/setup-ocaml@v2
+        uses: ocaml/setup-ocaml@v3
         with:
           ocaml-compiler: ${{ matrix.ocaml-version }}
           dune-cache: true