Upgrade Sphinx to 7.3.7

[kaxil]

closes #31963

All the linked issues on the above have been resolved

---

^ Add meaningful description above
Read the Pull Request Guidelines for more information.
In case of fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
In case of a new dependency, check compliance with the ASF 3rd Party License Policy.
In case of backwards incompatible changes please leave a note in a newsfragment file, named {pr_number}.significant.rst or {issue_number}.significant.rst, in newsfragments.

[kaxil]

One wrinkle:sphinx>=7.0.1 depends on docutils>=0.18.1,<0.21 and we have limited docutils to <0.17

airflow/hatch_build.py

Lines 160 to 163 in 9a0d9c5

	# Docutils 0.17.0 converts generated <div class="section"> into <section> and breaks our doc formatting
	# By adding a lot of whitespace separation. This limit can be lifted when we update our doc to handle
	# <section> tags for sections
	"docutils<0.17,>=0.16",

[kaxil]

Other related issue/PR:

• Fix Sphinx Airflow Theme to work for Sphinx 7 airflow-site#843

[potiuk]

FYI @kaxil .

From what I remember (see my old PR) the biggest problem there was to make appropriate changes to the theme so that the document "look" right. The change in docutils needed means that the generated documentation has a different HTML structure (different tags are used to construct the headers etc. ) and we need to update/rebuild CSS and release a new theme to make it looks good (and do it in the way to not break past released documentation as the theme is shared).

[kaxil]

From what I remember (see my old PR) the biggest problem there was to make appropriate changes to the theme so that the document "look" right. The change in docutils needed means that the generated documentation has a different HTML structure (different tags are used to construct the headers etc. ) and we need to update/rebuild CSS and release a new theme to make it looks good (and do it in the way to not break past released documentation as the theme is shared).

Yeah, I looked at the PR in apache/airflow-site#843, planning to circle back and check with @utkarsharma2 too on the CSS changes and stuff. Not immediately but hopefully we can fix this soon'ish