mark generated version header
mark generated version header

Allows it to pass the license check in chromium.

BUG=chromium:98319

Change-Id: I5ba9c8c81ab9eb4168df09db9d2eab846e99e981

webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx