roll: third_party/pigweed pw_channel: Remove WriteToken

This API required some extra implementation and user complexity to
track exactly how far a channel has pushed data, but really the caller
needs to invoke the PendWrite method regardless until it returns
Ready in order to ensure that all writes actually occur.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/245932
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Original-Revision: bd17ed6971f608e2d66da8b2954bc13ad3e2c664

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 5e44b4ebf5730a..bd17ed6971f608
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8732496046529204065
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I1a2f4d02878df482e3aed13b211d1adbb159e7b4
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/246014
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.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 5e44b4e..bd17ed6 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 5e44b4ebf5730a144e4924331429bb0084a94bd3
+Subproject commit bd17ed6971f608e2d66da8b2954bc13ad3e2c664