[roll] Roll fuchsia [debroot] Use Packages.xz files

Some newer dists only have Packages.xz, not Packages.gz.
The older dists have both.  The .xz file is always smaller.

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/584379
Original-Revision: bb0e68c123fd57bc400187b9799cbba770a5e100
GitOrigin-RevId: c12c069bca03c3565d448f17758bdee7c6748cdc
Change-Id: I6d1190210bcf74d076f807b426c88420155c250c
diff --git a/stem b/stem
index cd7951d..45bc3b6 100644
--- a/stem
+++ b/stem
@@ -10,7 +10,7 @@
              githooks=""
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="885b91719e9c0257d9822189a63a8d5f358ffbcb"/>
+             revision="bb0e68c123fd57bc400187b9799cbba770a5e100"/>
   </projects>
   <hooks>
     <hook name="install-environment"