[bugfix] Fix the incorrect path to the test document in positional-nested.xql
[bugfix] Fix the incorrect path to the test document in positional-nested.xql

RemiKoutcherawy/exist,RemiKoutcherawy/exist,RemiKoutcherawy/exist,RemiKoutcherawy/exist,RemiKoutcherawy/exist,RemiKoutcherawy/exist