R1:ada4f65565a0

Stop sending Phriction edit mail to the previous/current content author

Summary:
See <https://discourse.phabricator-community.org/t/previous-author-of-phriction-page-always-receives-mail-when-new-author-edits-the-page/1155>.

After the "send users email when they are removed from the reviewer list" change which includes old To/Cc on the list, Phriction now emails the previous editor.

This is weird and unintended. The behavior isn't necessarily always bad, but if it's sometimes desirable we should make it…