Check if C++ tests now work with ffmpeg6

Author: NicolasHug

.github/workflows/cpp_tests.yaml

@@ -24,10 +24,10 @@ jobs:
       - name: Check out repo
         uses: actions/checkout@v3
       - name: Setup conda env
-        uses: conda-incubator/setup-miniconda@v3
+        uses: conda-incubator/setup-miniconda@v2
         with:
           auto-update-conda: true
-          miniforge-version: latest
+          miniconda-version: "latest"
           activate-environment: test
           python-version: '3.12'
       - name: Update pip