[llvm] [docs] remove some out-of-date content in LLVM Programmer's Manual (PR #74989)

[Yuhao Gu via llvm-commits]

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@@ -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.
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yhgu2000 wrote:

I added these comments to let someone blame me in the future.

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