send-email: use (?:) instead of () if no match variables are needed

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>

git-send-email.perl

@@ -365,7 +365,7 @@ my(%suppress_cc);
 if (@suppress_cc) {
 	foreach my $entry (@suppress_cc) {
 		die "Unknown --suppress-cc field: '$entry'\n"
-			unless $entry =~ /^(all|cccmd|cc|author|self|sob|body|bodycc)$/;
+			unless $entry =~ /^(?:all|cccmd|cc|author|self|sob|body|bodycc)$/;
 		$suppress_cc{$entry} = 1;
 	}
 }