[roll third_party/pigweed] pw_transfer: Fix when to write Chunk::PendingBytes

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/98521

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: d7431f4e1a0acf7..cf60b1cddba0b89
Roller-URL: https://ci.chromium.org/b/8811076019236445633
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8811076019236445633
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I062d8313b323aa79c31d0cc0de7ddd87a6c116f8
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/98586
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index d7431f4..cf60b1c 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit d7431f4e1a0acf7c8e63f011ec2050d1f0b02149
+Subproject commit cf60b1cddba0b89b320e1f8dbff5e92a0525118b