Implement `(#.)` using `coerce` when possible

[RyanGlScott]

Currently, the internals of Data.Reflection define this:

reflection/fast/Data/Reflection.hs

Lines 667 to 668 in 493f3fe

	(#.) :: (b -> c) -> (a -> b) -> a -> c
	(#.) _ = unsafeCoerce

On modern GHCs, we can implement this using coerce instead. See here for an example of how to do this.