Raise the bar with regards to Python and Sphinx requirements

This series increases the minimal requirements for Sphinx and Python, and drop some backward-compatible code from Sphinx extension.

Looking at Sphinx release dates:

	Release 2.4.0 (released Feb 09, 2020)
	Release 2.4.4 (released Mar 05, 2020) (current minimal requirement)
	Release 3.4.0 (released Dec 20, 2020)
	Release 3.4.3 (released Jan 08, 2021)

	(https://www.sphinx-doc.org/en/master/changes/index.html)

And Python release dates, we have:

	Python	Release date 
	3.5	2015-09-13    (current minimal requirement)
	3.6	2016-12-23
	3.7 	2018-06-27
	3.8 	2019-10-14
	3.9 	2020-10-05
	3.10	2021-10-04

	(according with https://en.wikipedia.org/w/index.php?title=History_of_Python)

The new minimal requirements are now compatible with the toolset available on Jan, 2021, e.g.:
- Sphinx 3.4.3;
- Python 3.9

The new Sphinx minimal requirement allows dropping all backward-compatible code we have at kernel-doc and at Sphinx extensions.

The new Python minimal requirement also matches the current required level for almost all scripts (*).

Those matches a 4-years old toolchain, which sounds a reasonable period of time, as Python/Sphinx aren't required for the Kernel build.

(*) Except for a couple scripts inside tools that require python 3.10:

    $ vermin -v $(git ls-files '*.py')|grep 3.10
    !2, 3.10     tools/net/sunrpc/xdrgen/generators/__init__.py
    !2, 3.10     tools/net/sunrpc/xdrgen/generators/program.py
    !2, 3.10     tools/net/sunrpc/xdrgen/subcmds/source.py
    !2, 3.10     tools/net/sunrpc/xdrgen/xdr_ast.py
    !2, 3.10     tools/perf/scripts/python/mem-phys-addr.py
    !2, 3.10     tools/power/cpupower/bindings/python/test_raw_pylibcpupower.py

Such scripts aren't required for Kernel builds, so it should be OK to set minimal python version to 3.9.

Mauro Carvalho Chehab (4):
docs: changes: update Sphinx minimal version to 3.4.3
docs: changes: update Python minimal version
docs: extensions: don't use utf-8 syntax for descriptions scripts/kernel-doc: drop Sphinx version check

 Documentation/conf.py                       |   2 +-
 Documentation/process/changes.rst           |   4 +-
 Documentation/sphinx/cdomain.py             |   7 +-
 Documentation/sphinx/kernel_abi.py          |   6 +-
 Documentation/sphinx/kernel_feat.py         |   4 +-
 Documentation/sphinx/kernel_include.py      |   4 +-
 Documentation/sphinx/kerneldoc.py           |   5 -
 Documentation/sphinx/kfigure.py             |  10 +-
 Documentation/sphinx/load_config.py         |   2 +-
 Documentation/sphinx/maintainers_include.py |   4 +-
 Documentation/sphinx/rstFlatTable.py        |  10 +-
 scripts/kernel-doc                          | 129 +++-----------------
 12 files changed, 41 insertions(+), 146 deletions(-)

2.48.1