[roll third_party/pigweed] docs: Update module docs authoring guidelines

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/177465

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: e1835d3d9149ec6..9335766691d9ddd
Roller-URL: https://ci.chromium.org/b/8765502923908146033
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I8958db42ac5afff45c8ddcd533ec32bb9f73f0c1
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/178862
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 e1835d3..9335766 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit e1835d3d9149ec69350bb8e68cdadb53db066b7a
+Subproject commit 9335766691d9ddd8c44cd9116889af11506bbb9e