[roll third_party/pigweed] docs: Fix broken links

Original-Bug: b/299181944
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/169579

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: c90c2ab93a012dd..8af3cbcce3f0ff5
Roller-URL: https://ci.chromium.org/b/8770677706725917809
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I1f536cc0ec934fd422efe71d23b812b41ab2898f
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/169735
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 c90c2ab..8af3cbc 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit c90c2ab93a012dd32111f2cf92d7ccaac3559567
+Subproject commit 8af3cbcce3f0ff5bd08a51ceecae3f2395b0470b