[roll] Roll fuchsia [kernel][vm] Justify liveness of owner

Changes ProtectRangeFromReclamation to not assume that the owner lock
is held, but rather argues that holding the current child lock is
sufficient to guarantee that the raw owner pointer is live and able to
be dereferenced for the purposes of constructing a RefPtr.

Original-Bug: 338300943
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1250284
Original-Revision: 25d50dcac471f3b494c57a8cf6aeab7c183283be
GitOrigin-RevId: 38a230156834f20cdb52aa300878f2e9d94702d3
Change-Id: I24a05d5fcd973039d9fe1c4fdd64457aef15328c
diff --git a/stem b/stem
index d178627..4ddd4ca 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="ada96c6dc1c58e13cac62d42faa0b20a2e46be94"
+             revision="25d50dcac471f3b494c57a8cf6aeab7c183283be"
              />
   </projects>
   <hooks>