Review usage of `covdefaults` and `.coveragerc`

[tpvasconcelos]

Review the current state of the .coveragerc config file. My guess is that it could probably be simplified since we are also using the covdefaults package.

[tpvasconcelos]

While working on #161 I also noticed that blocks such as if sys.version_info >= (3, 10): are not ignored anymore (see .coveragerc)