[clang-format] Fix wrong indentation after trailing requires clause.

Fixes https://github.com/llvm/llvm-project/issues/52834.

Before this patch, clang-format would wrongly parse top-level entities (e.g. namespaces) and format:
```
template<int I>
constexpr void foo requires(I == 42) {}
namespace ns {
void foo() {}
}  // namespace ns
```
into:
``````
template<int I>
constexpr void foo requires(I == 42) {}
namespace ns {
  void foo() {}
}  // namespace ns
```
with configuration:
```
NamespaceIndentation: None
````

Reviewed By: MyDeveloperDay, HazardyKnusperkeks, owenpan

Differential Revision: https://reviews.llvm.org/D116183