[llvm] [docs] Kaleidoscope Tutorial Chapter 7 - base class Value* used for AllocaInst for assignment expression (PR #202101)

[Lang Hames via llvm-commits]

https://github.com/lhames commented:

This change isn't essential to the chapter, so I'm inclined to keep the code as-is. (The change of `NamedValues` elements to `AllocaInst*` is essential, and already reflected in the code).

In general I think we want to minimise differences between the code so that readers can focus on the essential changes only.

https://github.com/llvm/llvm-project/pull/202101