Try pinning micromamba

Author: mroeschke

.github/actions/setup-conda/action.yml

@@ -9,13 +9,15 @@ runs:
     - name: Install ${{ inputs.environment-file }}
       uses: mamba-org/setup-micromamba@v2
       with:
+        # Pinning to due solver performance regressions
+        micromamba-version: '2.1.0'
         environment-file: ${{ inputs.environment-file }}
         environment-name: test
         condarc-file: ci/.condarc
         cache-environment: true
         cache-downloads: true
-        cache-downloads-key: "foobar"
-        cache-environment-key: "foobar1"
+        cache-downloads-key: "foobar1"
+        cache-environment-key: "foobar2"
         log-level: trace
         create-args: --strict-channel-priority