[roll] Roll fuchsia [fidl][cpp] handle wire unknown events

Update wire types with support for handling unknown events. This works
essentially identically to how handling unknown events is done in
Natural Types, and uses the same interface.

Original-Bug: 88366
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/704013
Original-Revision: 81edfb36ccd1865b681e688278c20e3ff37d5033
GitOrigin-RevId: 333208f43593d2def0303af455eef09732b65201
Change-Id: I623b5e4d02f80fc4562933aa5f5c7d512a23adc2
diff --git a/stem b/stem
index a526928..512cfb1 100644
--- a/stem
+++ b/stem
@@ -10,7 +10,7 @@
              githooks=""
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="2400a607f5ef1f08f3770968ef28af494e61606a"/>
+             revision="81edfb36ccd1865b681e688278c20e3ff37d5033"/>
   </projects>
   <hooks>
     <hook name="install-environment"