Update which publication sub-types can be political
Update which publication sub-types can be political

"Research And Analysis" and "International Treaties" were initially
marked as political formats, but aren't anymore.

https://trello.com/c/rlJkchwi/124-remove-international-treaties-and-research-and-analysis-from-history-mode

This will require a reprocessing of political content, to apply
these new rules, which will happen separately (and after some
other changes to the rules for politicality of content).

Note: I've not updated any tests with this change. The tests assert
the behaviour of `political_publication_type`, rather than specific
publication types in `POLITICAL_PUBLICATION_TYPES` - so this change
passes the existing tests.

askl56/whitehall,hotvulcan/whitehall,ggoral/whitehall,alphagov/whitehall,hotvulcan/whitehall,askl56/whitehall,askl56/whitehall,YOTOV-LIMITED/whitehall,robinwhittleton/whitehall,ggoral/whitehall,YOTOV-LIMITED/whitehall,alphagov/whitehall,robinwhittleton/whitehall,YOTOV-LIMITED/whitehall,robinwhittleton/whitehall,ggoral/whitehall,YOTOV-LIMITED/whitehall,alphagov/whitehall,robinwhittleton/whitehall,askl56/whitehall,hotvulcan/whitehall,alphagov/whitehall,hotvulcan/whitehall,ggoral/whitehall