[doc] Contextualized warning in ACAS-Xu

doc/acas_xu.rst

@@ -206,6 +206,9 @@ We can write this as a predicate for clarity:
   original authors provide in their
   `repository <https://github.com/NeuralNetworkVerification/Marabou/tree/master/resources/properties>`_.
 
+  Future release of CAISAR will provide built-in normalization functions to bridge the gap between
+  requirements and the actual computations.
+
 We must then define the result of the application of ``nn_1_1`` on the inputs.
 The built-in function ``@@`` serves this purpose. Its type, ``nn -> vector 'a -> vector 'a``, describes what it does: given a neural network ``nn`` and an input vector ``x``, return the vector that is the result of the application of ``nn`` on ``x``.
 Note that thanks to type polymorphism, ``@@`` can be used to