Bump ocaml/setup-ocaml from 2 to 3 (#679)

* 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] <[email protected]>

* Update build.yml

---------

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Sora Morimoto <[email protected]>

.github/workflows/build.yml

@@ -38,11 +38,9 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Set-up OCaml
-        uses: ocaml/setup-ocaml@v2
+        uses: ocaml/setup-ocaml@v3
         with:
           ocaml-compiler: ${{ matrix.ocaml-compiler }}
-          allow-prerelease-opam: true
-          opam-depext: false
           opam-pin: false
 
       - run: opam pin add ocsigen-start.dev . --no-action