[roll] Roll fuchsia [ui][test] add kill scene_manager to flatland_benchmarks_test cleanup

Without kill scene_manager, `ffx session add` will fail
after dart version of flatland_benchmarks_test.

With this CL, lacewing version of flatland_benchmarks_test
does not require reboot fxr/890561.

Test: manual test in terminal product:
      fx test --e2e --output //src/tests/end_to_end/perf:flatland_benchmarks_test
      ffx session start
      ffx session add fuchsia-pkg://fuchsia.com/flatland-examples#meta/flatland-view-provider.cm

Original-Bug: b/295528505
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/901220
Original-Revision: f0a69e90e680e1961c0e031fa17744dbfbb8f681
GitOrigin-RevId: 019fb9c802a137c99eca88316b53a30a03b20749
Change-Id: I6eba9fdf13a9416348717a7f2eb8daebbbe39ca4
diff --git a/stem b/stem
index 5c192f1..b7a2069 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="1ef4e81386c97732ef09081784b1c954b0ad9ec7"/>
+             revision="f0a69e90e680e1961c0e031fa17744dbfbb8f681"/>
   </projects>
   <hooks>
     <hook name="install-environment"