Remove references of the #django IRC channel as a place to get help/place to promote things

[Sarah Boyce]

Forum discussion: ​https://forum.djangoproject.com/t/proposal-retire-irc/37129

We mention #django IRC channels in the Django docs and in various places on the Django website (such as in the footer, coc page, coc faq page).
We also have a step in our Django release process to update a topic in #django IRC.

As #django IRC is very quiet, we should reduce it's importance in terms of how many times we point users to it.
Having reviewed the docs, this would be almost completely removed from the docs (although I think to keep the reference in the security guide not to post to IRC).
On the Django website, we can keep IRC in the “More help” sidebar of the community page, similar to StackOverflow and Reddit, and remove the rest.

[Natalia Bidart]

Thank you!

[Sarah Boyce <42296566+sarahboyce@…>]

In 15e207c:

Fixed #35999 -- Removed #django IRC channel references where appropriate.

Some references are replaced with links to the Django Discord server.

[Sarah Boyce <42296566+sarahboyce@…>]

In 8d81c473:

[5.1.x] Fixed #35999 -- Removed #django IRC channel references where appropriate.

Some references are replaced with links to the Django Discord server.

Backport of 15e207ce80581ec64bd790c37cce1bc07d01a744 from main.