Updated checkout action

Author: ankane

.github/workflows/build.yml

@@ -4,7 +4,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: ocaml/setup-ocaml@v3
         with:
           ocaml-compiler: 5