[roll third_party/pigweed] pw_rpc: Include FakeChannelOutput in soong target

The implementation file `fake_channel_output.cc` was not included in the
src filegroup, which causes undefined symbol errors when used.

Original-Bug: 340350973
Test: Run tests on Android main which use fake channel output and ensure
no undefined symbol errors.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/209991
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 7e07cfabb7a8768..16fb026b93fcdad
Roller-URL: https://ci.chromium.org/b/8747725340459525809
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ic54493ab2ee59a839812317ae68badcae5598a15
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/210280
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 7e07cfa..16fb026 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 7e07cfabb7a8768c1676b138de7cc23996a3c924
+Subproject commit 16fb026b93fcdad596b7ffdadf368839d0c5235b