send-email: sanitize_address use $foo, not "$foo"

send-email: sanitize_address use $foo, not "$foo"

There's no reason to explicitly stringify a variable in Perl unless
it's an overloaded object and you want to call overload::StrVal,
otherwise it's just creating a new scalar redundantly.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.comReviewed-by: Avery Pennarun <apenwarr@gmail.com>
Reviewed-by: Jeff King <peff@peff.net>
>
Signed-off-by: Junio C Hamano <gitster@pobox.com>