Try setup ocaml

Author: richardpringle

.github/workflows/tests.yaml

@@ -259,6 +259,11 @@ jobs:
       - name: Setup build dependencies
         uses: ./.github/actions/setup-build-deps
 
+      - name: Use shared OCaml setting up steps
+        uses: ./.github/actions/setup-ocaml
+        with:
+          ocaml_version: ${{ env.OCAML_VERSION }}
+
       - name: Setup Rust
         uses: ./.github/actions/setup-rust
         with: