docs: networking: devlink-trap: Fix reference to other document

This fixes the following Sphinx warning:

Documentation/networking/devlink-trap.rst:175: WARNING: unknown document: /devlink-trap-netdevsim

Fixes: 9e08745704 ("Documentation: Add description of netdevsim traps")
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/networking/devlink-trap.rst

@@ -172,7 +172,7 @@ help debug packet drops caused by these exceptions. The following list includes
 links to the description of driver-specific traps registered by various device
 drivers:
 
-  * :doc:`/devlink-trap-netdevsim`
+  * :doc:`devlink-trap-netdevsim`
 
 Generic Packet Trap Groups
 ==========================