Don't add author and reviewers to CCs in Herald

Summary:
Herald rules are adding CC also for Author and Reviewer.
See also D1397.
I was considering also just don't displaying the extra CC but this is probably better.

There are still cases where there could be reviewer in CC (e.g. by making reviewer from CC or by direct edit) but I think it's not a big problem.

Beeing both Reviewer and CC can be actually useful (e.g. if you resign than you still are in CC) but it's not that useful to justify this:

Author: vrana
Reviewers: epriestley
CCs: vrana, epriestley

Test Plan: Comment on revision where I am author.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D2057