wix: restore COPYING.rtf
This got truncated to 0 bytes in
0ab651b5f77c when the Phabricator extension
crashed because it's a binary file. That caused the license page in the WIX
installer to be empty. I don't remember if I needed to resubmit after the bug
was fixed, so let's try this again with the current stable. If this fails, I'll
retry with 5.1 to see if this is a regression in the API changeover last cycle.
Differential Revision: https://phab.mercurial-scm.org/D8052
== New Features ==
== New Experimental Features ==
== Bug Fixes ==
== Backwards Compatibility Changes ==
== Internal API Changes ==