roll: third_party/pigweed: pw_rpc: Fix typing in unaryWait return value in TS client

A branch ensures that a response exists, so it cannot be undefined.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/231071
Owners-Override: Alexei Frolov <frolv@google.com>

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 917de4a88da5427..3c6179191f9d90d
Roller-URL: https://ci.chromium.org/b/8739039754597008705
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I4ad10e3e3f38fdf74acec39d0205a82deb365182
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/230741
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 917de4a..3c61791 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 917de4a88da542780acbc3a49ab1cae5de5ec1c0
+Subproject commit 3c6179191f9d90d45bf8dcaeecb8758aa9b23115