Update actions to use node 16

[ErichSuter]

Resolves #1189

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 80.02%. Comparing base (0375fed) to head (bc01c90). Report is 3 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1196 +/- ## ========================================== - Coverage 80.02% 80.02% -0.01% ========================================== Files 98 98 Lines 13680 13685 +5 Branches 2203 2204 +1 ========================================== + Hits 10948 10951 +3 - Misses 1999 2000 +1 - Partials 733 734 +1 ```

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