MAINT: Upgrade the remaining GitHub Actions. <!-- Thank you for contributing to Pyodide! All improvements are welcome,
     so don't be afraid to make a PR. -->

### Description

<!-- Please explain what your PR is about:
     - reasoning for the change
     - some details of updated code
     - any noteworthy choices to be aware of
	Please refer to any related issues by #<issue_id> -->

- https://github.com/actions/checkout/releases
- https://github.com/docker/build-push-action/releases
- https://github.com/docker/login-action/releases
- https://github.com/docker/metadata-action/releases
- https://github.com/pypa/gh-action-pypi-publish/releases
- https://github.com/test-summary/action/releases

Also, add a final check to the CPython upgrade instructions.

### Checklists

<!-- Note:
     If you think some of these steps are not necessary for your PR,
     remove those checkboxes, or mark them as checked. If you keep unchecked checkboxes,
     we will assume that your PR is not ready to be merged  -->

- [ ] Add a [CHANGELOG](https://github.com/pyodide/pyodide/blob/main/docs/project/changelog.md) entry
- [x] Add / update tests
- [ ] Add new / update outdated documentation

package:
  name: attrs
  version: 22.1.0
  top-level:
    - attr
    - attrs
source:
  sha256: 86efa402f67bf2df34f51a335487cf46b1ec130d02b8d39fd248abfd30da551c
  url: https://files.pythonhosted.org/packages/f2/bc/d817287d1aa01878af07c19505fafd1165cd6a119e9d0821ca1d1c20312d/attrs-22.1.0-py2.py3-none-any.whl
requirements:
  run:
    - six
about:
  home: https://www.attrs.org/
  PyPI: https://pypi.org/project/attrs
  summary: Classes Without Boilerplate
  license: MIT

package:
  name: attrs
  version: 22.1.0
  top-level:
    - attr
    - attrs
source:
  sha256: 86efa402f67bf2df34f51a335487cf46b1ec130d02b8d39fd248abfd30da551c
  url: https://files.pythonhosted.org/packages/f2/bc/d817287d1aa01878af07c19505fafd1165cd6a119e9d0821ca1d1c20312d/attrs-22.1.0-py2.py3-none-any.whl
requirements:
  run:
    - six
about:
  home: https://www.attrs.org/
  PyPI: https://pypi.org/project/attrs
  summary: Classes Without Boilerplate
  license: MIT
