docs: kernel-docs: shorten the lengthy doc title

The original title comes from copying the content from a web page that
covered various mixed computer-science material. Within the kernel
documentation and its current structure, the title can be shortened.

Other titles considered, but not selected were:
  - Index of More Kernel Documentation
  - Further Kernel Documentation
  - References to Further Kernel Documentation

Shorten the title.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20220704122537.3407-3-lukas.bulwahn@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/process/kernel-docs.rst

@@ -1,7 +1,7 @@
 .. _kernel_docs:
 
-Index of Documentation for People Interested in Writing and/or Understanding the Linux Kernel
-=============================================================================================
+Index of Further Kernel Documentation
+=====================================
 
           Juan-Mariano de Goyeneche <jmseyas@dit.upm.es>