This is one of the specifications of the Test Server, all objects have that watermark when they are used in this kind of server, and there's no way to get rid of them.
Check the Server Reference Manual "par. 19.6 Test license" onwards for further reference:
19.6 Test License A special license type has been created for use with QlikView Server for test purposes. A QVS running with such a license will have the full feature set and performance, but the word "Test" will be superimposed on all charts and added to all object captions.
Hope that helps.