[roll third_party/pigweed] pw_sync: Fix the bazel build

The build was broken only because the BUILD file referred to a couple
nonexistent files.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/98261

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 55b450bcdc4eead..b641ad950547e2c
Roller-URL: https://ci.chromium.org/b/8811258493207426145
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8811258493207426145
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I9c9587159e2c160f2ce50496fa9fd6bfc325e202
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/98280
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 55b450b..b641ad9 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 55b450bcdc4eead4bbe7178e7c2e3d08a79d5afa
+Subproject commit b641ad950547e2c56e8be154087f27b8291b1846