Fix some edge strings; particularly revision editing

Summary:
These didn't get translated quite right:

• We need to use $total_count because some languages have different words for 1, 2-3, and 4+ things (for example). So the strings might translate as:
  • alincoln added a reviewer-one ...
  • alincoln added reviewers-few ...
  • alincoln added reviewers-many ...
• That is, while English has only "reviewer" and "reviewers", other languages have more plural forms, and "reviewer", "reviewers-few" and "reviewers-many" may be completely different words.
• In English, because we know we always have 2+ in this branch and the only special word is for 1, we can just drop this.
• Anyway, the %4$s stuff is counting assuming that $total_count is included in the string, so these were a off by one.
• See also D11160.

There a probably a couple more of these, but they should be easy enough to hunt down as they crop up.

Test Plan: Saw nice strings instead of empty strings, or invalid strings (after D11160).

Reviewers: joshuaspence, btrahan

Reviewed By: btrahan

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D11162