fix(filterFilter): filter deep object by string

Before #9757 and 1.3.6, filterFilter with string expression used to check object's properties recursively. Now it checks only object's top level properties, which is a breaking change to existing applications.

Here is a test that this pull request makes passable.

```js
  it('should filter deep object by string', function() {
    var items = [{person: {name: 'Annet', email: 'annet@example.com'}},
                 {person: {name: 'Billy', email: 'me@billy.com'}},
                 {person: {name: 'Joan', email: {home: 'me@joan.com', work: 'joan@example.net'}}}];
    expect(filter(items, 'me@joan').length).toBe(1);
    expect(filter(items, 'joan@example').length).toBe(1);
  });
```