Remove polish (its not supported) and Bulgarian only has lite stemming.

Summary:
This says Bulgarian only has "lite" stemming.
http://docs.aws.amazon.com/cloudsearch/latest/developerguide/text-processing.html

Test Plan:
Ran it for real and it finished.
python provision-domain.py khan-academy-prod-2 domain-info.yaml

Reviewers: benkomalo

Reviewed By: benkomalo

Differential Revision: http://phabricator.khanacademy.org/D14086