fix: fix casing for z-index
fix: fix casing for z-index

The CSS-property z-index had some faulty casings. Only occurs in src/ol/ol.css
stweil/openlayers,oterral/ol3,bjornharrtell/ol3,openlayers/openlayers,openlayers/openlayers,stweil/openlayers,ahocevar/openlayers,oterral/ol3,bjornharrtell/ol3,oterral/ol3,ahocevar/openlayers,ahocevar/openlayers,bjornharrtell/ol3,openlayers/openlayers,stweil/openlayers