[clang] [clang] Cleanup docs and code for legacy no_sanitize attributes (NFC). (PR #161311)

[Erich Keane via cfe-commits]

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@@ -582,6 +582,7 @@ Moved checkers
 
 Sanitizers
 ----------
+- Fixed documentation for legacy ``no_sanitize`` attributes.
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erichkeane wrote:

```suggestion
- Improved documentation for legacy ``no_sanitize`` attributes.
```

https://github.com/llvm/llvm-project/pull/161311