[llvm] [RemoveDIs] Add documentation for IR debug records (PR #81156)

[Felipe de Azevedo Piovezan via llvm-commits]

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@@ -8510,7 +8511,10 @@ The LLVM instruction set consists of several different classifications
 of instructions: :ref:`terminator instructions <terminators>`, :ref:`binary
 instructions <binaryops>`, :ref:`bitwise binary
 instructions <bitwiseops>`, :ref:`memory instructions <memoryops>`, and
-:ref:`other instructions <otherops>`.
+:ref:`other instructions <otherops>`. There are also :ref:`debug records
+<debugrecords>`, which are not true instructions themselves but are printed
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felipepiovezan wrote:

brevity: ~~true~~

https://github.com/llvm/llvm-project/pull/81156