[clang-tools-extra] [clang-tidy] In bugprone-unused-return-value allow cast to void for pre-C++26 by default (PR #171618)

[via cfe-commits]

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@@ -153,6 +153,12 @@ Improvements to clang-tidy
   `-header-filter='.*'`. To disable warnings from non-system, set `-header-filter`
   to an empty string.
 
+- :doc:`bugprone-unused-return-value <clang-tidy/checks/bugprone/unused-return-value>`
+  now defaults ``AllowCastToVoid`` to ``false`` when running with C++26 or newer
+  language modes, while older standards keep the previous ``true`` default.
+  With C++26, the ``_`` placeholder should be used to mark unused return
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EugeneZelenko wrote:

```suggestion
  now defaults `AllowCastToVoid` to `false` when running with C++26 or newer
  language modes, while older standards keep the previous `true` default.
  With C++26, the `_` placeholder should be used to mark unused return
```

https://github.com/llvm/llvm-project/pull/171618