[roll] Roll fuchsia [netstack3] Squash NUD buffer trait variants

Squash buffer trait variants into their non-buffer counterparts.

Bubble up bounds on <S as Serializer>::Buffer instead of taking an extra
B type parameter on the loopback module while I'm here.

Original-Bug: 135142
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/953857
Original-Revision: 2087644da319cba182a9f18e9940dec4d0bf9131
GitOrigin-RevId: 6a521192d0bfc16eab6129cec43cce682d264abc
Change-Id: Ic1fccaf0613ff335e0ed80bb37571d083cf477a5
diff --git a/stem b/stem
index b0496d8..741caa9 100644
--- a/stem
+++ b/stem
@@ -11,7 +11,7 @@
              githooks="integration/git-hooks"
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="165510e369e7109f13b203bbfb95f469501283ec"/>
+             revision="2087644da319cba182a9f18e9940dec4d0bf9131"/>
   </projects>
   <hooks>
     <hook name="install-environment"