doc: update list archive reference to use lore.kernel.org

No disrespect to other mailing list archives, but the local part of
their URLs will become pretty much meaningless once the archives go
out of service, and we learned the lesson hard way when $gmane
stopped serving.

Let's point into https://lore.kernel.org/ for an article that can be
found there, because the local part of the URL has the Message-Id:
that can be used to find the same message in other archives, even if
lore goes down.

Signed-off-by: Junio C Hamano <[email protected]>

Author: gitster

Documentation/CodingGuidelines

@@ -24,7 +24,7 @@ code.  For Git in general, a few rough rules are:
 
    "Once it _is_ in the tree, it's not really worth the patch noise to
    go and fix it up."
-   Cf. http://lkml.iu.edu/hypermail/linux/kernel/1001.3/01069.html
+   Cf. https://lore.kernel.org/all/20100126160632.3bdbe172.akpm@linux-foundation.org/
 
  - Log messages to explain your changes are as important as the
    changes themselves.  Clearly written code and in-code comments