gating.yaml: duplicate the stanzas
The Gating spec used to recommend having one type of
YAML stanza for master, one for released branches. We
just discovered today that this breaks when master
forks into a release branch: the string 'stable'
needs to be manually changed to 'testing', and
nobody is going to remember to do that, and I can't
think of a (non-tedious) way to add automated checks.
As of 2019-08 (09d7d4f), though, the Gating spec suggests
having *both* stanzas together in the same gating.yaml
file. @pingou himself concurs. Although this is
horrible duplication -- two hundred characters, repeated
with only six of those different -- it seems cleaner
than the maintenance burden of having to update
Oh, also, add a new 'subject_type' line apparently "required"
even though things seem to have been working fine without it.
(Source: same commit, 09d7d4f, on gating.adoc).
Signed-off-by: Ed Santiago <email@example.com>