mailmap: Add entry for Joe Damato

My Fastly email address is no longer used. Add a mailmap entry to
reflect that.

Signed-off-by: Joe Damato <joe@dama.to>
Link: https://patch.msgid.link/20260303024202.2526604-1-joe@dama.to
Signed-off-by: Jakub Kicinski <kuba@kernel.org>