setup-ocaml 3.1.4 (fix darcs not found) (#7202)

Author: cknitt

.github/workflows/ci.yml

@@ -151,7 +151,7 @@ jobs:
       # matrix.ocaml_compiler may contain commas
       - name: Get OPAM cache key
         shell: bash
-        run: echo "opam_cache_key=opam-env-v5-${{ matrix.os }}-${{ matrix.ocaml_compiler }}-${{ hashFiles('dune-project') }}" | sed 's/,/-/g' >> $GITHUB_ENV
+        run: echo "opam_cache_key=opam-env-v6-${{ matrix.os }}-${{ matrix.ocaml_compiler }}-${{ hashFiles('dune-project') }}" | sed 's/,/-/g' >> $GITHUB_ENV
 
       - name: Restore OPAM environment
         id: cache-opam-env
@@ -167,7 +167,7 @@ jobs:
           key: ${{ env.opam_cache_key }}
 
       - name: Use OCaml ${{matrix.ocaml_compiler}}
-        uses: ocaml/setup-ocaml@v3.0.15
+        uses: ocaml/setup-ocaml@v3.1.4
         if: steps.cache-opam-env.outputs.cache-hit != 'true'
         with:
           ocaml-compiler: ${{matrix.ocaml_compiler}}