d/changelog: fix format typo
d/changelog: fix format typo

When building, this produces:

dpkg-source: warning: tools-manifest-0.12/debian/changelog(l5): badly formatted trailer line
LINE:  -- Giovanni Tirloni <gtirloni@wikimedia.org> Mon, 26 Nov 2018 00:00:00 +0000

Change-Id: I12c30ed5a3200508770f7b9712ca11a816c30432
Signed-off-by: Arturo Borrero Gonzalez <08787c72be15fc0aaf7bfde37e2aab5e1957f12a@wikimedia.org>

wikimedia/operations-software-tools-manifest