release: Push 19.3 back two weeks

release: Push 19.3 back two weeks

The main reason to do this is that 19.2 has slipped by two weeks, and
such the 19.3 branch is due to happen extremely close to the release of
19.2.0. I think it would be better to have a little more time between
releases for developers and for packagers.

This would still have the 19.3 release out before December, even if it
slips by 1 week.

Acked-By: Karol Herbst <kherbst@redhat.com>
Acked-by: Juan A. Suarez <jasuarez@igalia.com>