[clangd] Fix getQueryScopes for using-directive with inline namespace

For example, in the following code

```

using namespace std::string_literals;

int main() {
    strin^ // Completes `string` instead of `std::string`
}
```

The using declaration would make completion drop the std namespace, even though it shouldn't.

printNamespaceScope() skips inline namespaces, so to fix this use
printQualifiedName() instead

See https://github.com/clangd/clangd/issues/1451

Differential Revision: https://reviews.llvm.org/D140915