[llvm] [code-format] Also include libc++ extensionless headers (PR #73142)

[via llvm-commits]

================
@@ -126,13 +126,18 @@ def should_be_excluded(self, path: str) -> bool:
             return True
         return False
 
+    def should_include_extensionless_file(self, path: str) -> bool:
+        return path.startswith('libcxx/include')
----------------
philnik777 wrote:

```suggestion
        return path.startswith("libcxx/include")
```
To make the formatter happy.

https://github.com/llvm/llvm-project/pull/73142