[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