Update cache.rst

*Using Cache Tags* section has invalid example. Should use TagAwareCacheInterface.

Author: pavelmaca

cache.rst

@@ -486,15 +486,15 @@ to be able to invalidate the cache more efficient. One way to achieve that is to
 use cache tags. One or more tags could be added to the cache item. All items with
 the same key could be invalidate with one function call::
 
-    use Symfony\Contracts\Cache\ItemInterface;
+    use Symfony\Contracts\Cache\TagAwareCacheInterface;
 
-    $value0 = $pool->get('item_0', function (ItemInterface $item) {
+    $value0 = $pool->get('item_0', function (TagAwareCacheInterface $item) {
         $item->tag(['foo', 'bar'])
 
         return 'debug';
     });
 
-    $value1 = $pool->get('item_1', function (ItemInterface $item) {
+    $value1 = $pool->get('item_1', function (TagAwareCacheInterface $item) {
         $item->tag('foo')
 
         return 'debug';