[roll] Roll fuchsia [ffx_trace] Filter for "kernel:ipc" when symbolizing

A non kernel trace provider could emit a flow with an id with conflicts
with an ipc flow id. This could cause an id to be contained in the
`flow_state` mapping which points to a non-step containing kernel:ipc
flow, and a step containing non kernel:ipc flow which would trigger the
assert.

This filters non "kernel:ipc" events before attempting to check for flow
stages.

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1271144
Original-Revision: 787b28968c4e45cae3ee482c7ab38952e2494865
GitOrigin-RevId: c5394e4f554ffcd513b0a7029936b25e2bee1c0e
Change-Id: I715d1390a9bda2eec33f3a8d1e8cb4927c9bd589

stem

diff --git a/stem b/stem
index c143dc0..a6647c5 100644
--- a/stem
+++ b/stem
@@ -8,7 +8,7 @@
              root=""
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="ff8a57e0b50a5f8b4356b0f6a01161cba93c1f60"
+             revision="787b28968c4e45cae3ee482c7ab38952e2494865"
              />
   </imports>
   <projects>