[llvm] [Docs] Instructions for new contributors to find reviewers (PR #71936)

[Pablo Antonio Martinez via llvm-commits]

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@@ -98,7 +98,10 @@ To make sure the right people see your patch, please select suitable reviewers
 and add them to your patch when requesting a review. Suitable reviewers are the
 code owner (see CODE_OWNERS.txt) and other people doing work in the area your
 patch touches. Github will normally suggest some reviewers based on rules or
-people that have worked on the code before.
+people that have worked on the code before. If you are a new contributor, you
+will not be able to select reviewers in such way, in which case you can still
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pabloantoniom wrote:

Done, thanks for the tip

https://github.com/llvm/llvm-project/pull/71936