mailmap: update email address of Matheus Tavares

I haven't been very active in the community lately, but I'm soon going
to lose access to my previous commit email (@usp.br); so add my current
personal address to mailmap for any future message exchanges or patch
contributions.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.mailmap

@@ -165,6 +165,7 @@ Mark Rada <marada@uwaterloo.ca>
 Martin Langhoff <martin@laptop.org> <martin@catalyst.net.nz>
 Martin von Zweigbergk <martinvonz@gmail.com> <martin.von.zweigbergk@gmail.com>
 Masaya Suzuki <masayasuzuki@google.com> <draftcode@gmail.com>
+Matheus Tavares <matheus.tavb@gmail.com> <matheus.bernardino@usp.br>
 Matt Draisey <matt@draisey.ca> <mattdraisey@sympatico.ca>
 Matt Kraai <kraai@ftbfs.org> <matt.kraai@amo.abbott.com>
 Matt McCutchen <matt@mattmccutchen.net> <hashproduct@gmail.com>