correct micromamba workflow

.github/workflows/tests.yml

@@ -11,10 +11,15 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Setup Micromamba
-        uses: mamba-org/provision-with-micromamba@v16
+        uses: mamba-org/setup-micromamba
         with:
           environment-file: tests/environment.yml
-
+        uses: mamba-org/setup-micromamba@v1
+        with:
+          environment-file: tests/environment.yml
+        create-args: >- # beware the >- instead of |, we don't split on newlines but on spaces
+          python=${{matrix.python-version}}
+        cache-environment: true
       - name: Python ${{ matrix.python-version }}
         run: >
           micromamba activate pyglider-test