Rename ManiphestTransactionPro -> ManiphestTransaction

Summary: Ref T2217. Pro is the new standard.

Test Plan: Lots of `grep`, made a pile of Maniphest views/edits.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2217

Differential Revision: https://secure.phabricator.com/D7093