docs: sphinx: remove kernellog.py file

In the past, there was a need for a wrapper due to different
Sphinx versions support (before Sphinx 1.6). This is long gone,
and now it is just a wrapper. Get rig of it to simplify
the code.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/48bf16f199250d7048ca164d1b90773861915157.1739182025.git.mchehab+huawei@kernel.org