docs: process/index.rst: Fix reference to nonexistent document

Fix the following warning:

WARNING: toctree contains reference to nonexistent document
'process/unaligned-memory-access'

The path to the document was wrong.
Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
Link: https://lore.kernel.org/r/20200718165107.625847-5-dwlsalmeida@gmail.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/process/index.rst

@@ -61,7 +61,7 @@ lack of a better place.
    botching-up-ioctls
    clang-format
    ../riscv/patch-acceptance
-   unaligned-memory-access
+   ../core-api/unaligned-memory-access
 
 .. only::  subproject and html