Update codecov-action to v4 (node 16 to node 20 migration)

[mcbarton]

An action was missed when upgrading them in https://github.com/compiler-research/CppInterOp/pull/236 due to the migration of node 16 to node 20 in Github actions

[codecov[bot]]

Codecov Report

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

Project coverage is 79.40%. Comparing base (f93e7b6) to head (76692b9). Report is 4 commits behind head on main.

Additional details and impacted files

[](https://app.codecov.io/gh/compiler-research/CppInterOp/pull/250?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=compiler-research) ```diff @@ Coverage Diff @@ ## main #250 +/- ## ========================================== - Coverage 87.65% 79.40% -8.25% ========================================== Files 4 8 +4 Lines 1742 2982 +1240 ========================================== + Hits 1527 2368 +841 - Misses 215 614 +399 ``` [see 8 files with indirect coverage changes](https://app.codecov.io/gh/compiler-research/CppInterOp/pull/250/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=compiler-research) [see 8 files with indirect coverage changes](https://app.codecov.io/gh/compiler-research/CppInterOp/pull/250/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=compiler-research)

[mcbarton]

@alexander-penev can you merge this PR?

[vgvassilev]

Thanks!