Yes, that indeed fixes the warning.
I would like to help you by eliminating all of the respective warnings and making a PR, but when updating from the latest JUCE release’s modules folder to the develop branch’s latest tip, it doesn’t build anymore…
/Users/work/Documents/JUCE/modules/juce_video/native/juce_mac_Video.h:223:52: No type or protocol named 'NSKeyValueChangeKey'
This is probably related to macOS 10.13 Deployment Target: AU build fails.
I’m starting to believe there’s something terribly wrong with my setup…