sagemathgh-38091: Fix doctest when the optional benzene is installed

    
```
**********************************************************************
File "src/sage/features/__init__.py", line 384, in
sage.features.Feature.hide
Failed example:
    len(list(graphs.fusenes(2)))  # optional - benzene, needs
sage.graphs
Expected nothing
Got:
    1
**********************************************************************
1 item had failures:
   1 of   6 in sage.features.Feature.hide
    [146 tests, 1 failure, 3.74 s]
**********************************************************************
```

Comes from 1ade282
    
URL: sagemath#38091
Reported by: Volker Braun
Reviewer(s):

src/sage/features/__init__.py

@@ -382,6 +382,7 @@ def hide(self):
 
             sage: Benzene().unhide()            # optional - benzene, needs sage.graphs
             sage: len(list(graphs.fusenes(2)))  # optional - benzene, needs sage.graphs
+            1
         """
         self._hidden = True