Skip linkcheck on app.readthedocs.org/projects/pynwb URLs

[h-mayorquin]

The Sphinx linkcheck CI job has been intermittently failing on the two app.readthedocs.org/projects/pynwb/... URLs introduced in #2166 (docs/source/make_a_release.rst and docs/source/software_process.rst). The URLs themselves are valid and return 200 OK from a normal browser or local curl, but GitHub Actions runners frequently get throttled or blocked at readthedocs' CDN layer and receive 403s instead. Same failure mode as the existing scicrunch.org entry, so I added an analogous linkcheck_ignore pattern scoped to app\.readthedocs\.org/projects/pynwb/.*. I scoped it to the pynwb project specifically (rather than a broad app.readthedocs.org/* like the scicrunch entry uses) so that any future readthedocs URL elsewhere in the docs still gets caught by linkcheck if it ever points at a typo or a removed project.

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 ruff check . && codespell 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 95.18%. Comparing base (9231882) to head (d489755).

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #2191   +/-   ##
=======================================
  Coverage   95.18%   95.18%           
=======================================
  Files          30       30           
  Lines        2991     2991           
  Branches      444      444           
=======================================
  Hits         2847     2847           
  Misses         86       86           
  Partials       58       58           

Flag	Coverage Δ
integration	73.05% <ø> (ø)
unit	85.59% <ø> (ø)

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