[roll] Roll fuchsia [kernel][phys] Use ArchPanicReset() in test mains

This change brings the QEMU and devicetree test mains into line with the
ZBI and EFI ones. Previously we would just call `abort()` there, but
better to call `ArchPanicReset()` for a nicer shutdown.
(`ArchPanicReset` was not around at the time the qemu test main was
written, and the devicetree test main may have cargo-culted its
`abort()`.)

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1266120
Original-Revision: d4a1e2307dffa042e54712c35a27aa319b4b6cb0
GitOrigin-RevId: ea86cf5f49750755d6d9e2391b7025af8ac13fe7
Change-Id: Iefc94ddccb2c9d8b11e9eb600b741b9b2ae18782
diff --git a/stem b/stem
index b9d52a3..b491cad 100644
--- a/stem
+++ b/stem
@@ -8,7 +8,7 @@
              root=""
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="d7bc5b70b87eb7fda1e59d45f8f76d389080267d"
+             revision="d4a1e2307dffa042e54712c35a27aa319b4b6cb0"
              />
   </imports>
   <projects>