There are 2 walk around to remove this watermark
Method One :
Download the Microsoft update which will fix this issue, just download the file which is just a few kilo bytes and run it. Once the installation is complete restart the device and there you are.. water mark removed!
If method one doesn’t work this will surely work, press + R and when the run dialogue box appears type in the following
navigate to the following loaction
In the right panel, look for the word named “EnableLUA”
Double click on “EnableLUA” and change the value data from “1” to “0”
That will do the work, you will be prompted to restart the PC. Once restarted you will find the watermark long gone.
For any further doubts comment below. Enjoy.