docs: accounting: update delay-accounting.rst reference

The file name: accounting/delay-accounting.rst
should be, instead: Documentation/accounting/delay-accounting.rst.

Also, there's no need to use doc:`foo`, as automarkup.py will
automatically handle plain text mentions to Documentation/
files.

So, update its cross-reference accordingly.

Fixes: fcb5017045 ("delayacct: Document task_delayacct sysctl")
Fixes: c3123552aa ("docs: accounting: convert to ReST")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/sysctl/kernel.rst

@@ -1099,7 +1099,7 @@ task_delayacct
 ===============
 
 Enables/disables task delay accounting (see
-:doc:`accounting/delay-accounting.rst`). Enabling this feature incurs
+Documentation/accounting/delay-accounting.rst. Enabling this feature incurs
 a small amount of overhead in the scheduler but is useful for debugging
 and performance tuning. It is required by some tools such as iotop.