[lldb][docs] Remove dead link in toctree

Fixes warning:
index.rst:144: WARNING: toctree contains reference to nonexisting document 'use/python'

There used to be such a page but the URL now redirects
to "script-driven-debugging" which is in the "Python Reference"
section.

Author: DavidSpickett

lldb/docs/index.rst

@@ -146,7 +146,6 @@ interesting areas to contribute to lldb.
    :maxdepth: 1
    :caption: Scripting LLDB
 
-   use/python
    use/python-reference
    Python API <python_api>
    Python Extensions <python_extensions>