docs: sparse: add sparse.rst to toctree

docs: sparse: add sparse.rst to toctree

[ Upstream commit c9ad95adc096f25004d4192258863806a68a9bc8 ]

Add sparst.rst to toctree, so it can be part of the docs build.

Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Suggested-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Min-Hua Chen <minhuadotchen@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20230902052512.12184-4-minhuadotchen@gmail.com
Stable-dep-of: c48a7c44a1d0 ("docs: kernel_feat.py: fix potential command injection")
Signed-off-by: Sasha Levin <sashal@kernel.org>