bpo-37760: Mark all generated Unicode data headers as generated. (GH-15171)


This causes them to be collapsed by default in diffs shown on GitHub.

https://bugs.python.org/issue37760

Automerge-Triggered-By: @benjaminp
(cherry picked from commit 4e3dfcc4b987e683476a1b16456e57d3c9f581cb)

Co-authored-by: Greg Price <gnprice@gmail.com>