fix(pubsub): remove messages from leasing on nackWithResponse

[feywind]

Re-opening a fix for this in the new repo.

Fixes #7625 🦕

[pearigee]

This is a super nit of me, but Google's unit test best practices (see go/unit-testing-practices?polyglot=typescript#structure) recommend that unit tests be structured into clear arrange, act, and assert steps with whitespace.

I think that would make your test look like this:

      const stub = sandbox.stub(subscriber, 'modAckWithResponse');
      
      await subscriber.nackWithResponse(message);

      const [msg, deadline] = stub.lastCall.args;
      assert.strictEqual(msg, message);
      assert.strictEqual(deadline, 0);