Update codecov action

[codecov[bot]]

Codecov Report

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

Project coverage is 81.31%. Comparing base (9e1bf0d) to head (3b348f6).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2921 +/- ## ========================================== - Coverage 89.79% 81.31% -8.48% ========================================== Files 30 48 +18 Lines 30399 37856 +7457 Branches 5909 7295 +1386 ========================================== + Hits 27296 30782 +3486 - Misses 1778 5653 +3875 - Partials 1325 1421 +96 ``` | [Flag](https://app.codecov.io/gh/tskit-dev/tskit/pull/2921/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | Coverage Δ | | |---|---|---| | [c-tests](https://app.codecov.io/gh/tskit-dev/tskit/pull/2921/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | `86.21% <ø> (ø)` | | | [lwt-tests](https://app.codecov.io/gh/tskit-dev/tskit/pull/2921/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | `80.78% <ø> (ø)` | | | [python-c-tests](https://app.codecov.io/gh/tskit-dev/tskit/pull/2921/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | `67.71% <ø> (ø)` | | | [python-tests](https://app.codecov.io/gh/tskit-dev/tskit/pull/2921/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | `98.96% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev#carryforward-flags-in-the-pull-request-comment) to find out more. [see 31 files with indirect coverage changes](https://app.codecov.io/gh/tskit-dev/tskit/pull/2921/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev)