mailmap: Add another line for myself.

Signed-off-by: Nils Gillmann <gillmann@infotropique.org>
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

.mailmap

@@ -43,6 +43,7 @@ Mathieu Lirzin <mthl@gnu.org> <mathieu.lirzin@openmailbox.org>
 Mathieu Othacehe <m.othacehe@gmail.com>
 Nikita Karetnikov <nikita@karetnikov.org> <nikita.karetnikov@gmail.com>
 Nils Gillmann <ng0@n0.is> ng0 <ng0@n0.is>
+Nils Gillmann <ng0@n0.is> Nils Gillmann <gillmann@infotropique.org>
 Nils Gillmann <ng0@n0.is> ng0 <ng0@crash.cx>
 Nils Gillmann <ng0@n0.is> ng0 <ng0@crash.cx>
 Nils Gillmann <ng0@n0.is> <ng0@infotropique.org>