docs: move the link to the glossary to the front page rather than hiding it in the user guide.

docs/index.rst

-
 Welcome to Cython's Documentation
 =================================
 
@@ -10,6 +9,7 @@ Also see the `Cython project homepage <https://cython.org/>`_.
    src/quickstart/index
    src/tutorial/index
    src/userguide/index
+   src/userguide/glossary
    src/reference/index
    Contributing <CONTRIBUTING>
    src/changes

docs/src/userguide/index.rst

@@ -32,7 +32,3 @@ Indices and tables
 * :ref:`genindex`
 * :ref:`modindex`
 * :ref:`search`
-
-.. toctree::
-
-   glossary