[roll third_party/pigweed] docs: Update changelog

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/164810

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: b8d6d511016b2e8..e81ae0345b268ce
Roller-URL: https://ci.chromium.org/b/8772757700858041009
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I0263544ef8d12eb9768b26ffba1ea402364e5010
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/166031
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index b8d6d51..e81ae03 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit b8d6d511016b2e86a987a475bcf5a53f1beae290
+Subproject commit e81ae0345b268ce6036530ffb641fd56cf60b2c7