Further simplify instances to avoid overkill *1 classes

[Ericson2314]

free/src/Control/Monad/Free.hs

Line 148 in ca7982b

instance (Eq1 f, Eq a) => Eq (Free f a) where

For example I think could be

deriving instance (Eq a, Eq (f (Free f a))) => Eq (Free f a)

And even prior to quantified constraints, the solver can coinductively solve such constraints.