Documentation: fix links to mailing list services

There have been some changes to the way mailing lists are hosted at
kernel.org. This patch does the following:

1. fixes links that are pointing at the outdated resources
2. removes an outdated patchbomb admonition

We still don't particularly want or welcome huge patchbombs, but they
are less likely to overload our systems.

Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Reviewed-by: Carlos Bilbao <carlos.bilbao.osdev@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240619-docs-patch-msgid-link-v2-1-72dd272bfe37@linuxfoundation.org