Add cache for pixi tests

Author: sanders41

.github/workflows/testing.yml

@@ -430,7 +430,8 @@ jobs:
         uses: prefix-dev/[email protected]
         with:
           manifest-path: ${{ env.WORKING_DIR }}/pyproject.toml
-          pixi-version: v0.30.0
+          pixi-version: v0.57.0
+          cache: true
       - name: Set up Python
         working-directory: ${{ env.WORKING_DIR }}
         run: pixi add python=="${{ env.MIN_PYTHON_VERSION }}.*"
@@ -465,7 +466,8 @@ jobs:
         uses: prefix-dev/[email protected]
         with:
           manifest-path: ${{ env.WORKING_DIR }}/pyproject.toml
-          pixi-version: v0.30.0
+          pixi-version: v0.57.0
+          cache: true
       - name: Set up Python
         working-directory: ${{ env.WORKING_DIR }}
         run: pixi add python=="${{ env.MIN_PYTHON_VERSION }}.*"