Cast return value of removeItem() to boolean in delete()

In cases where an exception handler is in place, it's possible for a
null/void to be returned instead of a boolean. Casting it to boolean
will ensure a boolean false is returned, which is what we want.

src/Psr/SimpleCache/SimpleCacheDecorator.php

@@ -140,7 +140,7 @@ public function delete($key)
         }
 
         try {
-            return $this->storage->removeItem($key);
+            return (bool) $this->storage->removeItem($key);
         } catch (Throwable $e) {
             return false;
         } catch (Exception $e) {