fix CI

Author: yforster

.github/workflows/build.yml

@@ -22,7 +22,7 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Set-up OCaml ${{ matrix.ocaml-compiler }}
-        uses: ocaml/setup-ocaml@v2
+        uses: ocaml/setup-ocaml@v3
         with:
           ocaml-compiler: ${{ matrix.ocaml-compiler }}