mailmap: update manpage link

Patch series "Update .mailmap for my work address and fix manpage".

While updating mailmap for the going-away address, I also found that on
current systems the manpage linked from the header comment changed.

And in fact it looks like the git mailmap feature got its own manpage.


This patch (of 2):

On recent systems the git-shortlog manpage only tells people to
    See gitmailmap(5)

So instead of sending people on a scavenger hunt, put that info into the
header directly.  Though keep the old reference around for older systems.

Link: https://lkml.kernel.org/r/20230704163919.1136784-1-heiko@sntech.de
Link: https://lkml.kernel.org/r/20230704163919.1136784-2-heiko@sntech.deSigned-off-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

.mailmap

@@ -5,7 +5,8 @@
 # same person appearing not to be so or badly displayed. Also allows for
 # old email addresses to map to new email addresses.
 #
-# For format details, see "MAPPING AUTHORS" in "man git-shortlog".
+# For format details, see "man gitmailmap" or "MAPPING AUTHORS" in
+# "man git-shortlog" on older systems.
 #
 # Please keep this list dictionary sorted.
 #