mailmap: update Duje Mihanović's email address

I'm switching to a new mail address, so map my old one to it.

Link: https://lkml.kernel.org/r/20250620-mailmap-v1-1-a6b4b72dbd07@dujemihanovic.xyz
Signed-off-by: Duje Mihanović <duje@dujemihanovic.xyz>
Cc: Karel Balej <balejk@matfyz.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: LegoLivesMatter

.mailmap

@@ -223,6 +223,7 @@ Dmitry Safonov <0x7f454c46@gmail.com> <d.safonov@partner.samsung.com>
 Dmitry Safonov <0x7f454c46@gmail.com> <dsafonov@virtuozzo.com>
 Domen Puncer <domen@coderock.org>
 Douglas Gilbert <dougg@torque.net>
+<duje@dujemihanovic.xyz> <duje.mihanovic@skole.hr>
 Ed L. Cashin <ecashin@coraid.com>
 Elliot Berman <quic_eberman@quicinc.com> <eberman@codeaurora.org>
 Enric Balletbo i Serra <eballetbo@kernel.org> <enric.balletbo@collabora.com>