chore: Replace ts-prune with knip (#2595)

- Closes: #2593

tests/utils/thumbnail.test.ts

@@ -1,5 +1,5 @@
 import { Task } from '@lit-labs/task';
-import type { ReactiveControllerHost } from '@lit/reactive-element';
+import type { ReactiveControllerHost } from 'lit';
 import { afterEach, assert, describe, expect, it, vi } from 'vitest';
 import { mock } from 'vitest-mock-extended';