scripts: sphinx-pre-install: Address issues with OpenSUSE Leap 15.x

scripts: sphinx-pre-install: Address issues with OpenSUSE Leap 15.x

On openSUSE Leap 15.6, which is the current LTS version, has two
Sphinx packages. The normal one requires Python 3.6, which we
don't support anymore. However, it also has Python 3.11 with a
newer Sphinx version (7.2.6).

Suggest the newer version:

        Detected OS: openSUSE Leap 15.6.
        ERROR: at least python 3.7 is required to build the kernel docs
        Warning: python version is not supported.
        Warning: better to also install "convert".
        Warning: better to also install "dot".
        ERROR: please install "yaml", otherwise, build won't work.
        You should run:

                sudo zypper install --no-recommends ImageMagick graphviz python311-pyyaml

        Sphinx needs to be installed either:
        1) via pip/pypi with:

           Currently not possible.

           Please upgrade Python to a newer version and run this script again

        2) As a package with:

                sudo zypper install --no-recommends python311-Sphinx

            Please note that Sphinx >= 3.0 will currently produce false-positive
           warning when the same name is used for more than one type (functions,
           structs, enums,...). This is known Sphinx bug. For more details, see:
                https://github.com/sphinx-doc/sphinx/pull/8313

        Can't build as 2 mandatory dependencies are missing

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/a1600e292b63f96f40163e350238812158ebd6c2.1754992972.git.mchehab+huawei@kernel.org