[OSGeoLive] Request review for presentation note

[Cameron Shorter]

Hi, I've added a note to our presentation noting that the slide note 
pop-ups only work in some browsers.

Trivial change (and I've checked the note appears in the browser on build).

Could someone please review and approve my change

https://github.com/OSGeo/OSGeoLive-doc/pull/578

-- 
Cameron Shorter
Technology Demystifier
Open Technologies and Geospatial Consultant

M +61 (0) 419 142 254