fix inconsistent header

doc/index.rst

 SCS Toolbox
 ===========
 
+.. toctree::
+   :caption: Contents:
+   :maxdepth: 2
+
+   howtos.rst
+   maintainers.rst
+   changelog.rst
+
 Installation
 ------------
 
@@ -115,18 +123,9 @@ kernel or the ``xfel`` kernel if the toolbox was manually installed. For quick
 startup, example notebooks (.ipynb files) can be directly downloaded from the
 :ref:`How to's` section by clicking on the ``View page source``.
 
-.. toctree::
-   :caption: Contents:
-   :maxdepth: 2
-   :hidden:
-
-   howtos.rst
-   maintainers.rst
-   changelog.rst
-
 
 Contribute
-~~~~~~~~~~
+----------
 
 For reasons of readability, contributions preferrably comply with the PEP8_ code structure guidelines.