GH: use higher version of ocaml for github actions

Author: sipma

.github/workflows/dune.yaml

@@ -16,7 +16,7 @@ jobs:
           - "5.1.1"
     steps:
     - uses: actions/checkout@v1
-    - uses: ocaml/setup-ocaml@v2
+    - uses: ocaml/setup-ocaml@v3
       with:
         ocaml-compiler: ${{ matrix.ocaml-compiler }}
     - name: Install dependencies

.github/workflows/makefiles.yaml

@@ -14,7 +14,7 @@ jobs:
           - "4.14.1"
     steps:
     - uses: actions/checkout@v1
-    - uses: ocaml/setup-ocaml@v2
+    - uses: ocaml/setup-ocaml@v3
       with:
         ocaml-compiler: ${{ matrix.ocaml-compiler }}
     - name: Install dependencies