NbSortHeaderComponent fires sort event twice

### Issue type

* [x] bug report
* [ ] feature request

### Issue description

**Current behavior:**
`NbSortHeaderComponent` fires `sort` event twice. The event is fired by two different click event listeners.

**Expected behavior:**
`NbSortHeaderComponent` shall listen to click event only once.

**Steps to reproduce:**
1. Use `nbSort` directive on an `nbTreeGrid` component
2. Apply the `(sort)` event on the element
3. Log each call in the passed method

**Related code:**
Issue illustrated in [this repo](https://github.com/alomardev/nebular-sort-header-component-issue).

### Other information:

**Environment**
```
Browsers: Firefox, Edge
---
Angular CLI: 13.3.4
Node: 16.13.1
npm: 8.8.0
OS: win32 x64
---
Angular: 13.3.5
@nebular/theme: 9.0.2
```