phabricator: update the protocol documentation
The branch property wasn't added to the hg:meta example when it was added to
the metadata in d49ab47be8a6. Additionally, properties in the Differential
Revision dict is a dinctionary, not a list. While here, also alphabetize the
responses from Phabricator because that's how it is being printed with
hg debugcallconduit, and this makes it easier to compare.
Differential Revision: https://phab.mercurial-scm.org/D8170