[stable] Documentation: sysctl: align cells in second content column

Several stable branches (4.14 to 5.15 inclusive) belatedly got backports of commit 1202cdd665315c ("Remove DECnet support from kernel"). This causes a minor regression for the documentation build, which was fixed upstream by:

commit 1faa34672f8a17a3e155e74bde9648564e9480d6 Author: Bagas Sanjaya bagasdotme@gmail.com Date: Wed Aug 24 10:58:04 2022 +0700

Documentation: sysctl: align cells in second content column

Please apply this to the affected branches.

Ben.