Hide or remove user-visible XXX notes from distutils doc (#13716).

Requested by Florent Xicluna with the rationale that they make the docs
look unfinished.  When I get to replace the XXX notes with the real info
for packaging, I’ll backport it.

Also removed a few XXX notes that were not visible in the HTML but could
waste contributors’ time by suggesting improvements that are never going
to happen for distutils.
1 file changed