False positive when using static expressions

The following minimal code triggers the rules "lit/binding-positions" and "lit/no-invalid-html", although it should be completely valid according to the lit documentation (https://lit.dev/docs/templates/expressions/#static-expressions).

```ts
import { html, literal, StaticValue } from 'lit/static-html.js';

const tag: StaticValue = literal`header`;
return html`<${tag} class="classes">Content`
```