Merge branch 'af_unix-remove-old-gc-leftovers'

Kuniyuki Iwashima says:

====================
af_unix: Remove old GC leftovers.

This is a follow-up series for commit 4090fa373f0e ("af_unix: Replace
garbage collection algorithm.") which introduced the new GC for AF_UNIX.

Now we no longer need two ugly tricks for the old GC, let's remove them.
====================

Link: https://lore.kernel.org/r/20240401173125.92184-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>