[clang] [clang] Add -Wmissing-designated-field-initializers (PR #81364)

[Aaron Ballman via cfe-commits]

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@@ -120,6 +120,10 @@ Non-comprehensive list of changes in this release
 New Compiler Flags
 ------------------
 
+- ``-Wmissing-designated-field-initializers``, grouped under ``-Wmissing-designated-field-initializers``.
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AaronBallman wrote:

```suggestion
- ``-Wmissing-designated-field-initializers``, grouped under ``-Wmissing-field-initializers``.
```

https://github.com/llvm/llvm-project/pull/81364