[clang] Fix contextual implicit conversions to int: with _Atomic (PR #203522)

[Aaron Ballman via cfe-commits]

================
@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 -triple x86_64-linux -Wunused -verify %s
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AaronBallman wrote:

```suggestion
// RUN: %clang_cc1 -verify %s
```
Do we need those?

https://github.com/llvm/llvm-project/pull/203522