Update coverage call, don't install in editable mode in testing

[rly]

Motivation

Follow-up to NeurodataWithoutBorders/nwbinspector#450 (comment)

https://setuptools.pypa.io/en/latest/userguide/development_mode.html says

Editable installs are not a perfect replacement for regular installs in a test environment. When in doubt, please test your projects as installed via a regular wheel. There are tools in the Python ecosystem, like tox or nox, that can help you with that (when used with appropriate configuration).

We use editable installs in testing in a couple places, mostly to help coverage find the sources, but we can configure that in pyproject.toml instead.

How to test the behavior?

Run all GitHub actions

Checklist

• Did you update CHANGELOG.md with your changes?
• Does the PR clearly describe the problem and the solution?
• Have you reviewed our Contributing Guide?
• Does the PR use "Fix #XXX" notation to tell GitHub to close the relevant issue numbered XXX when the PR is merged?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.70%. Comparing base (3146c97) to head (9be854b).

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #1107   +/-   ##
=======================================
  Coverage   88.70%   88.70%           
=======================================
  Files          45       45           
  Lines        9745     9745           
  Branches     2767     2767           
=======================================
  Hits         8644     8644           
  Misses        779      779           
  Partials      322      322           

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