Even more cleaning of documentation references

src/ifcopenshell-python/docs/introduction/how_to_contribute.rst

@@ -21,14 +21,15 @@ Python API documentation is autogenerated from docstrings present in the source
 code of the respective Python module.
 
 If you want to build the documentation locally, the documentation system uses
-`Sphinx <https://www.sphinx-doc.org/en/master/>`_. First, install the theme and
-theme dependencies:
+`Sphinx <https://www.sphinx-doc.org/en/master/>`_. First, install Sphinx and
+dependencies:
 
 .. code-block:: console
 
-    $ pip install furo
+    $ pip install sphinx
     $ pip install sphinx-autoapi
     $ pip install sphinx-copybutton
+    $ pip install furo
 
 Now you can generate the documentation: