get make docs-html working

[pdurbin]

What this PR does / why we need it:

We advertise make docs-html as a way to build the guides at https://guides.dataverse.org/en/6.7.1/contributor/documentation.html#building-the-guides-with-a-sphinx-docker-container-and-a-makefile

It stopped working when we added in Sphinx-Substitution-Extensions in #11477.

Which issue(s) this PR closes:

• Closes make docs-html doesn't work #11829

Special notes for your reviewer:

None.

Suggestions on how to test this:

Try it.

Does this PR introduce a user interface change? If mockups are available, please link/include them here:

No.

Is there a release notes update needed for this change?:

I don't think so.

Additional documentation:

None.

Related:

• Building guides: Python 3.10 required, try Docker first, custom titles, other tweaks #11831

[coveralls]

coverage: 23.541%. remained the same
when pulling 892193c on 11829-make-docs-html
into 08b9ec6 on develop.

[Copilot]

Pull Request Overview

This PR fixes the make docs-html command that was broken after adding Sphinx-Substitution-Extensions in #11477. The issue was that the Makefile's grep pattern for extracting the Sphinx version was too broad, matching multiple packages instead of just Sphinx itself.

• Updated the grep pattern in the Makefile to be more specific when extracting the Sphinx version
• Added a comment explaining the rationale for the more specific search pattern

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[jp-tosca]

Looks good, sent an update on the branch.