Remove the export kml button in IE9

Fix for https://github.com/geoadmin/mf-geoadmin3/issues/1866

(IE9 does not support file save functionality and thus can't export kml. Note however, that a drawing can be send by email in the feedback tool)
I think `msie`  can only be NaN or a number, but may be I'm wrong. and you are right we use `isNaN` in other places too. 

May be we should set it at false in gaBrowserSniffer when it's not an ie browser  (in tests we set `msie` to false), but it's another PR :)