Flaky Test: `WatchTest` (`after()` method)

[diegomarquezp]

Example run: https://github.com/googleapis/java-firestore/actions/runs/19343299245/job/55336969365

Error:    WatchTest.after:174 array lengths differed, expected.length=1 actual.length=0; arrays first differed at element [0]; expected:<database: "projects/test-project/databases/(default)"
add_target {
  query {
    parent: "projects/test-project/databases/(default)/documents"
    structured_query {
      from {
        collection_id: "coll"
      }
    }
  }
  resume_token: "token"
  target_id: 1
}
> but was:<end of array>

This happens across all versions of ci / units(xx).

Related code:

java-firestore/google-cloud-firestore/src/test/java/com/google/cloud/firestore/WatchTest.java

Lines 170 to 178 in fa47838

	@After
	public void after() {
	Object[] emptyArray = new Object[0];
	assertArrayEquals(exceptions.toArray(), emptyArray);
	assertArrayEquals(requests.toArray(), emptyArray);
	assertArrayEquals(documentSnapshots.toArray(), emptyArray);
	assertArrayEquals(querySnapshots.toArray(), emptyArray);
	listenerRegistration.remove();
	}