Impact of trace amounts of water on the stability of Micro-Pattern Gaseous Detectors measured in Ar-CO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si68.svg" display="inline" id="d1e520"><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math> (90-10)