perl: *.pm files should not have the executable bit

The Git::Mail::Address file added in bd869f67b9 ("send-email: add and use a local copy of Mail::Address", 2018-01-05) had the executable bit set. That bit should not be set for *.pm files. It breaks nothing but it is redundant and confusing as none of the other files have it and these files are never executed as stand-alone programs. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>