[llvm] [docs] remove some out-of-date content in LLVM Programmer's Manual (PR #74989)

[Yuhao Gu via llvm-commits]

================
@@ -2779,17 +2761,9 @@ obtaining it via iteration over some structure:
     if (it != inst->getParent()->end()) errs() << *it << "\n";
   }
 
-Unfortunately, these implicit conversions come at a cost; they prevent these
-iterators from conforming to standard iterator conventions, and thus from being
-usable with standard algorithms and containers.  For example, they prevent the
-following code, where ``B`` is a ``BasicBlock``, from compiling:
-
-.. code-block:: c++
-
-  llvm::SmallVector<llvm::Instruction *, 16>(B->begin(), B->end());
-
-Because of this, these implicit conversions may be removed some day, and
-``operator*`` changed to return a pointer instead of a reference.
+..
+  The part about implicit conversion from an iterator to a pointer is out of
+  date and has been removed.
----------------
yhgu2000 wrote:

> why not just delete it then?

When I went through the commit history to confirm the commit that removed `operator pointer()`, I used GitHub blame to find out who modified the code. I found that commits solely removing content are particularly difficult to locate, as they do not appear in GitHub blame. Therefore, I believe it's best for me to leave a comment here to ensure that someone in the future can blame me in case these revisions cause issues.

Do you think this is a good idea? Let me know your opinion.

https://github.com/llvm/llvm-project/pull/74989