[roll third_party/pigweed] docs: Update changelog

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/185259

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 5b32d8dc55c9ac1..f8c71146b855fd8
Roller-URL: https://ci.chromium.org/b/8761601485905043201
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I13830638500f2bfd31fb769bee5ef56989d0bab8
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/185283
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 5b32d8d..f8c7114 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 5b32d8dc55c9ac1776230ab7b24a5e0629d2ed55
+Subproject commit f8c71146b855fd81864247f48132bcfa59ec4c85