MAINT: Need to be explicit with action path while using pixi run too

I missed this in #96 but we need to be explicit while using `pixi run` too.

I was tripping into `could not find pixi.toml or pyproject.toml which is configured to use pixi` while on the `pixi run` step downstream.

action.yml

@@ -45,4 +45,4 @@ runs:
         INPUT_ANACONDA_NIGHTLY_UPLOAD_TOKEN: ${{ inputs.anaconda_nightly_upload_token }}
         INPUT_ANACONDA_NIGHTLY_UPLOAD_LABELS: ${{ inputs.anaconda_nightly_upload_labels }}
       run: |
-        pixi run ${{ github.action_path }}/upload_wheels.sh
+        pixi run --manifest-path ${{ github.action_path }}/pixi.toml ${{ github.action_path }}/upload_wheels.sh