Updated to sphinx 7.2.6 with setup and Makefile changes

[MikeSullivan7]

Issue

Closes #1961 and progresses #1981

Description

Sphinx has been updated to the newest version 7.2.* (7.2.6 currently).

The documentation is no longer built via python setup.py docs but is now done via make build-docs which uses sphinx directly and does not use the setup file. The old documentation related commands and functions in setup.py have been deleted to progress moving away from using the setup file. The setup file is still required to publish the docs and create release notes, etc.

Note: This was required as from Sphinx 7 onwards sphinx.setup_command.BuildDoc is depreciated.

Testing

Test that the documentation still builds correctly.

Acceptance Criteria

Delete the docs/build folder and then run make build-docs. Once done, the documentation should build as it did before in the docs/build folder.

[coveralls]

coverage: 75.633%. remained the same
when pulling 15238d9 on 1961_update_sphinx
into e9e6ff4 on main.