[roll third_party/pigweed] docs: Update README links

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/189731

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 9d700d34f4a9625..c3041bb8dec2b51
Roller-URL: https://ci.chromium.org/b/8757272317066457857
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I22c3e31b70836655774b28cb5628eb68843a1e9a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/190014
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 9d700d3..c3041bb 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 9d700d34f4a96257ea96eb2b37ae66883a810aea
+Subproject commit c3041bb8dec2b51897792bf01b63ad99a0fdfdc4