Adding syntax error

Author: Nyholm

cache.rst

@@ -15,7 +15,7 @@ The following example shows a typical usage of the cache::
     // The callable will only be executed on a cache miss.
     $value = $pool->get('my_cache_key', function (ItemInterface $item) {
         $item->expiresAfter(3600);
-
+        'abc'
         // ... do some HTTP request or heavy computations
         $computedValue = 'foobar';