gh-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 1ade282122269d5369d53c07cdf069984f89bd8a
URL: https://github.com/sagemath/sage/pull/38091
Reported by: Volker Braun
Reviewer(s):
