FGData Merge Request #300: Remove an always unsatisfied predicate to a now unset property (merged)

The Galaxy effect is having as a predicate a test to a property which is no longer set (/sim/rendering/shader-effects), probably because it is no longer used by any other effects. Therefore, the Gaalxy effect is always inactive.
This patch simply removes that test (but keeps the others on quality-level).

PS: This effect has been first implemented in next 2020.4.0, so I am just keeping it up to date with the ongoing changes (no backward compat issue)