[Chapel Merge] Remove some additional references to SourceForge

Branch: refs/heads/master
Revision: 5bc81d6
Author: bradcray
Log Message:

Merge pull request #16703 from bradcray/less-sourceforge-more-discourse

Remove some additional references to SourceForge

[reviewed by @ben-albrecht]

I was surprised to find how frequently our documentation still refers to
the SourceForge mailing lists, which I apparently overlooked when
converting things to Discourse this summer. Here, I point developers
to the Discourse forums instead and remove some other references to
the SourceForge mailing lists, making slight tweaks in the vicinity
while there.

I believe the remaining active references to SourceForge mailing lists
are our scripts which still send “all passing” cases to SourceForge.
Removing these cases will either require more significant changes to
the scripts, or sending them to some other dummy email address.

Modified Files:
M doc/rst/developer/bestPractices/ContributorInfo.rst
M doc/rst/developer/bestPractices/TestSystem.rst
M util/cron/nightly
M util/test/genGraphs.py

Compare: https://github.com/chapel-lang/chapel/compare/ec7039b76f40...5bc81d665641