Update GitHub Actions action versions

[jwodder]

We are currently using older versions of the updated GitHub Actions actions, and these older versions still use Node 12, which is deprecated.

[codecov]

Codecov Report

Base: 96.61% // Head: 96.61% // No change to project coverage 👍

Coverage data is based on head (0fe7574) compared to base (e7a1975).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #148   +/-   ##
=======================================
  Coverage   96.61%   96.61%           
=======================================
  Files          16       16           
  Lines        1623     1623           
=======================================
  Hits         1568     1568           
  Misses         55       55           

Flag	Coverage Δ
unittests	96.61% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[yarikoptic]

hm, in another PR it errored on Test without network / test (ubuntu-18.04, 3.8) here on windows-2019 but differently but for the same reason

ERROR: Could not install packages due to an OSError: HTTPSConnectionPool(host='files.pythonhosted.org', port=443): Max retries exceeded with url: /packages/dc/bf/5965230bf0547c5fa0005984564146dcc414e6e8b6349177eca413761013/pydantic-1.10.2-cp37-cp37m-win_amd64.whl (Caused by ConnectTimeoutError(<pip._vendor.urllib3.connection.HTTPSConnection object at 0x0000021F9B1F5E48>, 'Connection to files.pythonhosted.org timed out. (connect timeout=15)'))

which I don't think relate so merging. Thanks @jwodder