There is little purpose served in removing it at this stage, with a new build coming in three weeks - particularly on a leaked build.
However, I am aware that there are a couple of "hacks abavailable to do this, but, again, not a viable alternative for a test build.
This is the easiest way, without hacking:
Have a look in "Ease of Access Center" - Make the computer easier to see - Last item "Remove background images.
Unticked, will show watermark. ticked, All gone
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