Fix reST in NEWS, and remove NEWS.help (all committers should now know reST anyway, and for those who do not, there is Documenting Python.)

- The entry about shutil.copytree is just a revert of r84524 which
looks like an unfinished edition.
- The use of gender-neutral language (s/his/their/) removes the
implicit assumption that programmer == male (change agreed by Antoine).
- Other changes should be uncontroversial fixes.

I haven’t rewrapped under 80 lines to keep the diffs readable; I’ll
rewrap later.

descriptor is provided.  Patch by Pascal Chambon.

the memory consumption of said decoded objects when they use the same
strings as keys.

by the new (and simpler) DUP_TOP_TWO.  Performance isn't changed, but
our bytecode is a bit simplified.  Patch by Demur Rumed.

'once_registry'. This is bad as the warnings module had variables named
'defaultaction' and 'onceregistry' which are what people should be looking at
(technically those variables shouldn't be mucked with as they are undocumented,
but we all know better than to believe that isn't happening). So the variables
from _warnings have been renamed to come off as private and to avoid confusion
over what variable should be used.

Closes issue #9766. Thanks to Antoine Pitrou for the discovery.

Patch by Michele Orrù and Björn Lindqvist.

(it only runs as root, which is why nobody bothered about the failure)

in the posix module.  Patch by Marcin Bachry.