minor symfony#9736 Item key for deletion (Guikingone)

This PR was merged into the 3.4 branch.

Discussion
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Item key for deletion

Hi,

As the CacheItem return is key with `getKey()` method, it could be useful to use the method to delete the item.

Commits
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f59e8d8 (feat): Item key call for deletion

Author: javiereguiluz

components/cache/cache_invalidation.rst

@@ -48,6 +48,9 @@ you can invalidate the cached items by calling
     // if you know the cache key, you can also delete the item directly
     $cache->deleteItem('cache_key');
 
+    // If you don't remember the item key, you can use the getKey() method
+    $cache->deleteItem($item->getKey());
+
 Using tags invalidation is very useful when tracking cache keys becomes difficult.
 
 Tag Aware Adapters