fix: actions/cache version

Author: gadomski

.github/workflows/continuous-integration.yml

@@ -32,7 +32,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Set up conda cache
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ~/conda_pkgs_dir
           key: ${{ runner.os }}-conda-${{ hashFiles('**/environment.yml') }}