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 GitHub actions

Checklist

• Did you update CHANGELOG.md with your changes?
• Have you checked our Contributing document?
• Have you ensured the PR clearly describes the problem and the solution?
• Is your contribution compliant with our coding style? This can be checked running flake8 from the source directory.
• Have you checked to ensure that there aren't other open Pull Requests for the same change?
• Have you included the relevant issue number using "Fix #XXX" notation where XXX is the issue number? By including "Fix #XXX" you allow GitHub to close issue #XXX when the PR is merged.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.01%. Comparing base (376e6ab) to head (00f15b0).

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #1897   +/-   ##
=======================================
  Coverage   92.01%   92.01%           
=======================================
  Files          27       27           
  Lines        2619     2619           
  Branches      685      685           
=======================================
  Hits         2410     2410           
  Misses        139      139           
  Partials       70       70           

Flag	Coverage Δ
integration	72.81% <ø> (ø)
unit	83.92% <ø> (ø)

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