[clang-format] Fix QualifierOrder breaking the code with requires clause.

Fixes https://github.com/llvm/llvm-project/issues/53962.

Given the config:
```
BasedOnStyle: LLVM
QualifierAlignment: Custom
QualifierOrder: ['constexpr', 'type']
```

The code:
```
template <typename F>
  requires std::invocable<F>
constexpr constructor();
```
was incorrectly formatted to:
```
template <typename F>
  requires
constexpr std::invocable<F> constructor();
```
because we considered `std::invocable<F> constexpr` as a type, not recognising the requires clause.

This patch avoids moving the qualifier across the boundary of the requires clause (checking `ClosesRequiresClause`).

Reviewed By: HazardyKnusperkeks, owenpan

Differential Revision: https://reviews.llvm.org/D120309