Docs: Disable ePub as a temporary work-around

[benjaoming]

Work-around for #9816

Will merge into diataxis/main after.

[stsewd]

Also, any chance we can fix the warnings instead?

/home/docs/checkouts/readthedocs.org/user_builds/docs/checkouts/diataxis-main/docs/user/guides/git-integrations.rst:18: WARNING: Duplicate explicit target name: "webhook-integration-github".
/home/docs/checkouts/readthedocs.org/user_builds/docs/checkouts/diataxis-main/docs/user/guides/git-integrations.rst:41: WARNING: Duplicate explicit target name: "webhook-integration-bitbucket".
/home/docs/checkouts/readthedocs.org/user_builds/docs/checkouts/diataxis-main/docs/user/guides/git-integrations.rst:51: WARNING: Duplicate explicit target name: "webhook-integration-gitlab".

But I don't see any duplicates in that page, so maybe a bug with sphinx or the tabs extension.

[benjaoming]

Also, any chance we can fix the warnings instead?

#9816 is about finding a way to exclude certain warnings so the ePub build can go ahead despite of the warnings.

We could open an issue about fixing these warnings, but as I understand it from @humitos, we might have already decided in principle to replace sphinx-tabs with sphinx-design.

[benjaoming]

Replaced by #9866