Docs/process/index: Remove unsorted docs section

'Other material' section on 'process/index' is no more necessary since
we have 'staging/' directory.  Also all documents on the section has
moved to better places.  Remove the section.
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240624185312.94537-6-sj@kernel.org

Documentation/process/index.rst

@@ -107,13 +107,6 @@ developers:
    kernel-docs
    deprecated
 
-These are some overall technical guides that have been put here for now for
-lack of a better place.
-
-.. toctree::
-   :maxdepth: 1
-
-
 .. only::  subproject and html
 
    Indices