addons: fix compilation error

```--
  CC       addons/vorepository.lo
addons/vorepository.c: In function 'Close':
addons/vorepository.c:490:9: error: implicit declaration of function 'unlink' [-Werror=implicit-function-declaration]
cc1: some warnings being treated as errors
```

--
Signed-off-by: Francois Cartegnie <fcvlcdev@free.fr>

modules/misc/addons/vorepository.c

@@ -487,7 +487,7 @@ static void Close(vlc_object_t *p_this)
     addons_finder_t *p_finder = (addons_finder_t*) p_this;
     if ( p_finder->p_sys->psz_tempfile )
     {
-        unlink( p_finder->p_sys->psz_tempfile );
+        vlc_unlink( p_finder->p_sys->psz_tempfile );
         free( p_finder->p_sys );
     }
 }