b7ce24d095 (Turn `git serve` into a test helper, 2019-04-18) demoted git
serve from a builtin command to a test helper. As a result the
git-serve binary is no longer built and thus doesn't have to be ignored
anymore.
Signed-off-by: René Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>