parent resource should be a model in the generated tsp

[pshao25]

In test packages\extensions\openapi-to-typespec\test\arm-playwrighttesting, the parent resource for Quota is a string.

@parentResource("SubscriptionLocationResource")
model Quota is ProxyResource<QuotaProperties> {
  /**
   * The quota name.
   */
  @path
  @key("name")
  @segment("quotas")
  @visibility("read")
  name: QuotaNames;
}

Expected: it should be a model.