docs/guide: remove the warning for array resource exhaustion.

It is no longer relevant in a NIR world.

Author: whitequark

docs/guide.rst

@@ -809,10 +809,6 @@ Crucially, this means that any Python object can be added to an array; the only
 
     An array becomes immutable after it is indexed for the first time. The elements of the array do not themselves become immutable, but it is not recommended to mutate them as the behavior can become unpredictable.
 
-.. warning::
-
-    Each time an array proxy object with :py:`n` elements is used in an expression, it generates a multiplexer with :py:`n` branches. However, using :py:`k` of such array proxy objects in an expression generates a multiplexer with :py:`n**k` branches. This can generate extremely large circuits that may quickly exhaust the resources of the synthesis target or even the available RAM.
-
 .. note::
 
     Arrays, :class:`amaranth.hdl.Array`, are distinct from and serve a different function than :class:`amaranth.lib.data.ArrayLayout`.