Update Github action to use setup-ocaml@v3

Author: xavierleroy

.github/workflows/ci.yml

@@ -32,7 +32,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Set-up OCaml ${{ matrix.ocaml-version }}
-        uses: ocaml/setup-ocaml@v3.0.0-beta
+        uses: ocaml/setup-ocaml@v3
         with:
           ocaml-compiler: ${{ matrix.ocaml-version }}
           allow-prerelease-opam: true