chore: update coveragepy to 7.4.3

[oxidase]

The updated covergepy version contains a fix for nedbat/coveragepy#1733 which leads to sporadic issues

.../rules_python~~python~python_3_12_x86_64-unknown-linux-gnu_coverage/coverage/collector.py", line 511, in flush_data
    for fname, packeds in packed_data.items():
RuntimeError: dictionary changed size during iteration

[aignas]

Thanks for the contribution, could you please add a CHANGELOG.md entry (probably in the Changed section) to note that we are bumping the coverage.py version to address upstream bugs. Something like:

* Bump `coverage.py` to [7.4.3](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst#version-743--2024-02-23).

[oxidase]

@aignas added

[aignas]

Thanks!