Merge pull request #225 from ilankri/ci

[ci] Use the latest version of `actions/checkout`

Author: balat

.github/workflows/workflow.yml

@@ -30,7 +30,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Use OCaml ${{ matrix.ocaml-compiler }}
         uses: ocaml/setup-ocaml@v2