Documentation: consistently use spaces inside initializers

Documentation: consistently use spaces inside initializers

Our coding guide is inconsistent with how it uses spaces inside of
initializers (`struct foo bar = { something }`). While we mostly carry
the space between open and closing braces and the initialized members,
in one case we don't.

Fix this one instance such that we consistently carry the space. This is
also consistent with how clang-format formats such initializers.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>