and split line to make flake8 happy

Related to swh/devel/swh-web#4746

swh-webhooks package is detected as swh-web by the code of that function
but django is not installed when building standalone doc for this package.

Logos in the table listing the forges were taking too much space,
resulting in unfortunate line breaks in other columns. Let’s reduce
their width to a minimum instead.

Also remove the secondary sidebar to get some extra space.

Properly specify that generate_forge_list.py is used as an input when
generating the lister and loader tables. We also change how the script
is invoked to be sure to use the current version.

- use #E20026 as primary (SWH's red)
- use secondary color for main's page buttons
- use #52566D (light) / #DBDBDB (dark) secondary color

Refs. swh/infra/sysadm-environment#4825

The schedule-first-visits parameters was not exact

Refs. swh/infra/sysadm-environment#4813

Make clear that the “API reference” page is an index of our modules.
Add a pointer to the “interface” part of the landing page for people
wanting to learn how to interact with Software Heritage.

Closes #4740

To ease finding that page in the documentation. This transforms the chapter from the
onboarding mirror page to a link to that page.

So they can be reused more easily from the documentation.

Refs. swh/infra/sysadm-environment#4759

Some renaming were missing.

Refs. swh/infra/sysadm-environment#4794

As reference namespace is global, we need to make an extra effort to name
reference uniquely.

Without this step, services are not scheduled.

swh/infra/sysadm-environment#4794

This now also mentions the jenkins job to use to build docker image.

swh/infra/sysadm-environment#4794

Notably, this:
- fixes how to enable the ilo remote access
- agnostifies a bit some samples
- adds hint on how to exist the serial console
- mentions the need to store the root password in the credentials store

Refs. swh/infra/sysadm-environment#4808

Related to #4732

Even if our `tox.ini` is compatible with tox 3, the command line
format changed with tox 4. For consistency in layout, usage and
documentation, it seems best to update requirements to version 4.

See: https://tox.wiki/en/latest/upgrading.html#updating-usage-with-e

Now that we use PyData Sphinx Theme, we can get rid of the link
customization meant for the RTD theme. This leftover template
was breaking the build with PyData Sphinx Theme 0.13.0.

The README mentions that building everything via tox uses pifpaf
to run the required postgresql database. It feels like a good idea
to also add pifpaf to the command lines required for the manual builds.