Fix aura tooltips on panel entities.
Removed from the GUI interface in r20965 / rP20965, but its uses weren't checked (or ignored).
(https://code.wildfiregames.com/source/0ad/browse/ps/trunk/binaries/data/mods/public/gui/session/session.js;20965$998)
Reported by @Langbart
Based on a patch by: @Langbart
Differential revision: https://code.wildfiregames.com/D4648
Fixes #6387