drop some fluff from docs/index.md

Author: ablaom

docs/src/index.md

@@ -92,16 +92,6 @@ then overloading `obs` is completely optional. Plain iteration interfaces, with
 knowledge of the number of observations, can also be specified (to support, e.g., data
 loaders reading images from disk).
 
-## Hooks adding algorithm-generic functonality
-
-Given any training `data` consumed by `fit` (such as `data = (X, y)` in the example above)
-[`LearnAPI.features(algorithm, data)`](@ref input) tells us what part of `data` comprises
-*features*, which is something that can be passed onto to `predict` or `transform` (`X` in
-the example) while [`LearnAPI.target(algorithm, data)`](@ref), if implemented, tells us
-what part comprises the target (`y` in the example). By explicitly requiring such methods,
-LearnAPI.jl frees algorithms to consume data in multiple forms, including optimised,
-algorithm-specific forms, as described above.
-
 ## Learning more
 
 - [Anatomy of an Implementation](@ref): informal introduction to the main actors in a new